[PATCH][AArch64] Fix ICE due to store_pair_lanes

[Steve Ellcey]

FYI: Here is a cut down test case showing the failure:

int foo (void) { }
extern void plunk ();
int splat (void)
{
      static int once = 0;
      plunk (&once, foo);
}

% obj/gcc/gcc/cc1 -mabi=ilp32 -O2 -quiet x.i

during RTL pass: final
x.i: In function ‘splat’:
x.i:7:1: internal compiler error: in aarch64_print_address_internal, at config/aarch64/aarch64.c:5638
 }
 ^
0x14286c7 aarch64_print_address_internal
	/home/sellcey/gcc-spec-
ilp32/src/gcc/gcc/config/aarch64/aarch64.c:5638
0x1428d4b aarch64_print_operand_address
	/home/sellcey/gcc-spec-
ilp32/src/gcc/gcc/config/aarch64/aarch64.c:5735
0xb5fa93 output_address(machine_mode, rtx_def*)
	/home/sellcey/gcc-spec-ilp32/src/gcc/gcc/final.c:3905
0xb5f40b output_asm_insn(char const*, rtx_def**)
	/home/sellcey/gcc-spec-ilp32/src/gcc/gcc/final.c:3766
0xb5e0df final_scan_insn(rtx_insn*, _IO_FILE*, int, int, int*)
	/home/sellcey/gcc-spec-ilp32/src/gcc/gcc/final.c:3064
0xb5bfbb final(rtx_insn*, _IO_FILE*, int)
	/home/sellcey/gcc-spec-ilp32/src/gcc/gcc/final.c:2052
0xb60d27 rest_of_handle_final
	/home/sellcey/gcc-spec-ilp32/src/gcc/gcc/final.c:4490
0xb6110f execute
	/home/sellcey/gcc-spec-ilp32/src/gcc/gcc/final.c:4564
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.