rs6000: Remove redundant guard for float128 mode pattern

gcc/
	* config/rs6000/rs6000.md (mov<mode>cc, *mov<mode>cc_p10,
	*mov<mode>cc_invert_p10, *fpmask<mode>, *xxsel<mode>,
	@ieee_128bit_vsx_abs<mode>2, *ieee_128bit_vsx_nabs<mode>2,
	add<mode>3, sub<mode>3, mul<mode>3, div<mode>3, sqrt<mode>2,
	copysign<mode>3, copysign<mode>3_hard, copysign<mode>3_soft,
	@neg<mode>2_hw, @abs<mode>2_hw, *nabs<mode>2_hw, fma<mode>4_hw,
	*fms<mode>4_hw, *nfma<mode>4_hw, *nfms<mode>4_hw,
	extend<SFDF:mode><IEEE128:mode>2_hw, trunc<mode>df2_hw,
	trunc<mode>sf2_hw, fix<uns>_<IEEE128:mode><SDI:mode>2_hw,
	fix<uns>_trunc<IEEE128:mode><QHI:mode>2,
	*fix<uns>_trunc<IEEE128:mode><QHSI:mode>2_mem,
	float_<mode>di2_hw, float_<mode>si2_hw,
	float<QHI:mode><IEEE128:mode>2, floatuns_<mode>di2_hw,
	floatuns_<mode>si2_hw, floatuns<QHI:mode><IEEE128:mode>2,
	floor<mode>2, ceil<mode>2, btrunc<mode>2, round<mode>2,
	add<mode>3_odd, sub<mode>3_odd, mul<mode>3_odd, div<mode>3_odd,
	sqrt<mode>2_odd, fma<mode>4_odd, *fms<mode>4_odd, *nfma<mode>4_odd,
	*nfms<mode>4_odd, trunc<mode>df2_odd, *cmp<mode>_hw for IEEE128):
	Remove guard FLOAT128_IEEE_P.
	(@extenddf<mode>2_fprs, @extenddf<mode>2_vsx,
	trunc<mode>df2_internal1, trunc<mode>df2_internal2,
	fix_trunc_helper<mode>, neg<mode>2, *cmp<mode>_internal1,
	*cmp<IBM128:mode>_internal2 for IBM128): Remove guard FLOAT128_IBM_P.