testsuite: Fix up pr104188.c testcase for i686-linux [PR104188]

testsuite: Fix up pr104188.c testcase for i686-linux [PR104188]

On i686-linux this new testcase FAILs with:
cc1: warning: SSE instruction set disabled, using 387 arithmetics
FAIL: gcc.target/i386/pr104188.c (test for excess errors)
Excess errors:
cc1: warning: SSE instruction set disabled, using 387 arithmetics
This is because it uses -mfpmath=sse, but -msse2 isn't on.  Fixed
by adding -msse2 to dg-options and requiring sse2_runtime effective
target.

2022-01-26  Jakub Jelinek  <jakub@redhat.com>

	PR target/104188
	* gcc.target/i386/pr104188.c: Add dg-require-effective-target
	sse2_runtime.  Add -msse2 to dg-options.