rs6000: Fix some unexpected empty split conditions

rs6000: Fix some unexpected empty split conditions

This patch is to fix empty split-conditions of some
define_insn_and_split definitions where their conditions for
define_insn part aren't empty.  As Segher and Mike pointed
out, they can sometimes lead to unexpected consequences.

Bootstrapped/regtested on powerpc64le-linux-gnu P9 and
powerpc64-linux-gnu P8.

gcc/ChangeLog:

	* config/rs6000/rs6000.md (*rotldi3_insert_sf,
	*mov<SFDF:mode><SFDF2:mode>cc_p9, floatsi<mode>2_lfiwax,
	floatsi<mode>2_lfiwax_mem, floatunssi<mode>2_lfiwzx,
	floatunssi<mode>2_lfiwzx_mem, *floatsidf2_internal,
	*floatunssidf2_internal, fix_trunc<mode>si2_stfiwx,
	fix_trunc<mode>si2_internal, fixuns_trunc<mode>si2_stfiwx,
	*round32<mode>2_fprs, *roundu32<mode>2_fprs,
	*fix_trunc<mode>si2_internal): Fix empty split condition.
	* config/rs6000/vsx.md (*vsx_le_undo_permute_<mode>,
	vsx_reduc_<VEC_reduc_name>_v2df, vsx_reduc_<VEC_reduc_name>_v4sf,
	*vsx_reduc_<VEC_reduc_name>_v2df_scalar,
	*vsx_reduc_<VEC_reduc_name>_v4sf_scalar): Likewise.