i386: Use assign_stack_temp instead of assign_386_stack_local with SLOT_TEMP

i386: Use assign_stack_temp instead of assign_386_stack_local with SLOT_TEMP

It is better to use assign_stack_temp instead of assign_386_stack_local
with SLOT_TEMP because assign_stack_temp also shares sub-space of stack
slots (e.g. HImode temp shares stack slot with SImode stack slot).

Use assign_386_stack_local only for special stack slots (SLOT_STV_TEMP that
can be nested inside other stack temp access, SLOT_FLOATxFDI_387 that has
relaxed alignment constraint) or slots that can't be shared (SLOT_CW_*).

The patch removes SLOT_TEMP. assign_stack_temp should be used instead.

	gcc/ChangeLog:

	* config/i386/i386.h (enum ix86_stack_slot): Remove SLOT_TEMP.
	* config/i386/i386-expand.cc (ix86_expand_builtin)
	<case IX86_BUILTIN_LDMXCSR>: Use assign_stack_temp instead of
	assign_386_stack_local with SLOT_TEMP.
	<case IX86_BUILTIN_LDMXCSR>: Ditto.
	(ix86_expand_divmod_libfunc): Ditto.
	* config/i386/i386.md (floatunssi<mode>2): Ditto.
	* config/i386/sync.md (atomic_load<mode>): Ditto.
	(atomic_store<mode>): Ditto.