xtensa: Fix non-robust split condition in define_insn_and_split

xtensa: Fix non-robust split condition in define_insn_and_split

This patch is to fix some non-robust split conditions in some
define_insn_and_splits, to make each of them applied on top of
the corresponding condition for define_insn part, otherwise the
splitting could perform unexpectedly.

gcc/ChangeLog:

	* config/xtensa/xtensa.md (movdi_internal, movdf_internal): Fix split
	condition.