AArch64: Remove shuffle pattern for rounding variant.

AArch64: Remove shuffle pattern for rounding variant.

This removed the patterns to optimize the rounding shift and narrow.
The optimization is valid only for the truncating rounding shift and narrow,
for the rounding shift and narrow we need a different pattern that I will submit
separately.

This wasn't noticed before as the benchmarks did not run conformance as part of
the run, which we now do and this now passes again.

gcc/ChangeLog:

	* config/aarch64/aarch64-simd.md (*aarch64_topbits_shuffle<mode>_le
	,*aarch64_topbits_shuffle<mode>_be): Remove.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/shrn-combine-8.c: Update.
	* gcc.target/aarch64/shrn-combine-9.c: Update.