aarch64: Add pattern for bswap + rotate [PR 110039]

After commit g:d8545fb2, we missed a
pattern to match the new GIMPLE form.

With this patch, gcc.target/aarch64/rev16_2.c passes again.

2023-05-31  Christophe Lyon  <christophe.lyon@linaro.org>

	PR target/110039
	gcc/
	* config/aarch64/aarch64.md (aarch64_rev16si2_alt3): New
	pattern.