middle-end/111253 - partly revert r11-6508-gabb1b6058c09a7

middle-end/111253 - partly revert r11-6508-gabb1b6058c09a7

The following keeps dumping SSA def stmt RHS during diagnostic
reporting only for gimple_assign_single_p defs which means
memory loads.  This avoids diagnostics containing PHI nodes
like

  warning: 'realloc' called on pointer '*_42 = PHI <lcs.14_40(29), lcs.19_48(30)>.t_mem_caches' with nonzero offset 40

instead getting back the previous behavior:

  warning: 'realloc' called on pointer '*<unknown>.t_mem_caches' with nonzero offset 40

	PR middle-end/111253
gcc/c-family/
	* c-pretty-print.cc (c_pretty_printer::primary_expression):
	Only dump gimple_assign_single_p SSA def RHS.

gcc/testsuite/
	* gcc.dg/Wfree-nonheap-object-7.c: New testcase.