testsuite: Fix pr55569.c excess errors on LLP64

testsuite: Fix pr55569.c excess errors on LLP64

This fixes the following on LLP64 mingw-w64 target:

Excess errors:
gcc/testsuite/gcc.c-torture/compile/pr55569.c:13:12: warning: overflow in conversion from 'long long unsigned int' to 'long int' changes value from '4611686018427387903' to '-1' [-Woverflow]
gcc/testsuite/gcc.c-torture/compile/pr55569.c:13:34: warning: iteration 2147483647 invokes undefined behavior [-Waggressive-loop-optimizations]

gcc/testsuite/ChangeLog:
	* gcc.c-torture/compile/pr55569.c: fix excess errors.

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