sh: Remove can_create_pseudo_p check

Optab instruction conditions are cached and so won't adapt to the
current phase of compilation.

The old code to FAIL for !create_pseudo_p was redundant since
general-purpose arithmetic optabs like bswap can only be used
while can_create_pseudo_p is true.

gcc/
	* config/sh/sh.md (bswapsi): Remove can_create_pseudo_p () check.