GCN: Enable effective-target 'vect_hw_misalign'

GCN: Enable effective-target 'vect_hw_misalign'

... as made apparent by commit 4e1fcf44bdc582e71408175d75e025f5be8b0e55
"testsuite: vect: Require vect_hw_misalign in gcc.dg/vect/vect-cost-model-1.c etc. [PR98238]"
causing:

     PASS: gcc.dg/vect/vect-cost-model-1.c (test for excess errors)
    -PASS: gcc.dg/vect/vect-cost-model-1.c scan-tree-dump vect "LOOP VECTORIZED"

     PASS: gcc.dg/vect/vect-cost-model-3.c (test for excess errors)
    -PASS: gcc.dg/vect/vect-cost-model-3.c scan-tree-dump vect "LOOP VECTORIZED"

     PASS: gcc.dg/vect/vect-cost-model-5.c (test for excess errors)
    -PASS: gcc.dg/vect/vect-cost-model-5.c scan-tree-dump vect "LOOP VECTORIZED"

..., and similarly commit ffd47fb63ddc024db847daa07f8ae27fffdfcb28
"testsuite: Fix pr113431.c FAIL on sparc* [PR113431]" causing:

     PASS: gcc.dg/vect/pr113431.c (test for excess errors)
     PASS: gcc.dg/vect/pr113431.c execution test
    -PASS: gcc.dg/vect/pr113431.c scan-tree-dump-times slp1 "optimized: basic block part vectorized" 2

..., which this commit all restores, and also enables a good number of further
FAIL -> PASS, UNSUPPORTED -> PASS, etc. progressions.  There are also a small
number of regressions, mostly in the SLP area apparently:

     PASS: gcc.dg/vect/bb-slp-layout-12.c (test for excess errors)
    +XPASS: gcc.dg/vect/bb-slp-layout-12.c scan-tree-dump-not slp1 "duplicating permutation node"
    +XFAIL: gcc.dg/vect/bb-slp-layout-12.c scan-tree-dump-times slp1 "add new stmt: [^\\n\\r]* = VEC_PERM_EXPR" 3

     PASS: gcc.dg/vect/bb-slp-layout-6.c (test for excess errors)
    +FAIL: gcc.dg/vect/bb-slp-layout-6.c scan-tree-dump slp2 "absorbing input layouts"

     PASS: gcc.dg/vect/pr97428.c (test for excess errors)
     PASS: gcc.dg/vect/pr97428.c scan-tree-dump vect "Detected interleaving load of size 8"
     PASS: gcc.dg/vect/pr97428.c scan-tree-dump vect "Detected interleaving store of size 16"
     PASS: gcc.dg/vect/pr97428.c scan-tree-dump-not vect "gap of 6 elements"
    -XFAIL: gcc.dg/vect/pr97428.c scan-tree-dump-times vect "vectorizing stmts using SLP" 2
    +FAIL: gcc.dg/vect/pr97428.c scan-tree-dump-times vect "vectorizing stmts using SLP" 2

     PASS: gcc.dg/vect/vect-33.c (test for excess errors)
    +FAIL: gcc.dg/vect/vect-33.c scan-tree-dump vect "Vectorizing an unaligned access"
     PASS: gcc.dg/vect/vect-33.c scan-tree-dump-not optimized "Invalid sum"
     PASS: gcc.dg/vect/vect-33.c scan-tree-dump-times vect "vectorized 1 loops" 1

..., so some further conditionalizing etc. seems necessary.  These seem to
mostly appear next to pre-existing similar FAILs in related test cases.
(Overall, way more PASS than FAIL.)

	gcc/testsuite/
	* lib/target-supports.exp
	(check_effective_target_vect_hw_misalign): Enable for GCN.
	(check_effective_target_vect_element_align): Adjust.