testsuite: Fix pr94185.C testcase on i686-linux with C++98 [PR94185]

testsuite: Fix pr94185.C testcase on i686-linux with C++98 [PR94185]

I'm getting on i686-linux
FAIL: g++.target/i386/pr94185.C  -std=gnu++98 (test for excess errors)
This is because of a diagnostic that 4294967295 is unsigned only in ISO C90.
Adding U suffix fixes it and the testcase still ICEs with unfixed gcc and
passes with current trunk.

2020-03-17  Jakub Jelinek  <jakub@redhat.com>

	PR target/94185
	* g++.target/i386/pr94185.C (l): Use 4294967295U instead of 4294967295
	to avoid FAIL with -m32 -std=c++98.