c-c++-common/Warray-bounds.c: Fix excess warnings on LLP64

c-c++-common/Warray-bounds.c: Fix excess warnings on LLP64

Excess errors on x86_64-w64-mingw32:
/home/user/p/gcc/src/gcc-git/gcc/testsuite/c-c++-common/Warray-bounds.c:50:3: warning: array subscript 4611686018427387902 is above array bounds of 'struct S16[]' [-Warray-bounds=]
/home/user/p/gcc/src/gcc-git/gcc/testsuite/c-c++-common/Warray-bounds.c:55:3: warning: array subscript 4611686018427387902 is above array bounds of 'struct S16[]' [-Warray-bounds=]
/home/user/p/gcc/src/gcc-git/gcc/testsuite/c-c++-common/Warray-bounds.c:90:3: warning: array subscript 658812288346769699 is above array bounds of 'struct S16[][7]' [-Warray-bounds=]

gcc/testsuite/ChangeLog:

	* c-c++-common/Warray-bounds.c: Fix excess warnings on
	LLP64.

Signed-off-by: Jonathan Yong <10walls@gmail.com>