i386: Optimize vpblendvb on inverted mask register to vpblendvb on swapping the order...

i386: Optimize vpblendvb on inverted mask register to vpblendvb on swapping the order of operand 1 and operand 2. [PR target/99908]

-       vpcmpeqd        %ymm3, %ymm3, %ymm3
-       vpandn  %ymm3, %ymm2, %ymm2
-       vpblendvb       %ymm2, %ymm1, %ymm0, %ymm0
+       vpblendvb       %ymm2, %ymm0, %ymm1, %ymm0

gcc/ChangeLog:

	PR target/99908
	* config/i386/sse.md (<sse4_1_avx2>_pblendvb): Add
	splitters for pblendvb of NOT mask register.

gcc/testsuite/ChangeLog:

	PR target/99908
	* gcc.target/i386/avx2-pr99908.c: New test.
	* gcc.target/i386/sse4_1-pr99908.c: New test.