[OpenACC] Remove (unused) 'GOMP_MAP_ALWAYS_FROM' handling from…

[OpenACC] Remove (unused) 'GOMP_MAP_ALWAYS_FROM' handling from 'libgomp/oacc-mem.c:goacc_exit_data_internal'

This had gotten added in commit 378da98f
(r279621) "OpenACC reference count overhaul", but it doesn't have any use in
OpenACC.

	libgomp/
	* oacc-mem.c (goacc_exit_data_internal): Remove
	'GOMP_MAP_ALWAYS_FROM' handling.

(cherry picked from commit 995aba5867b1c64b2b56a200ef16b135effe85f7)

libgomp/oacc-mem.c

@@ -1102,7 +1102,6 @@ goacc_exit_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 	{
 	case GOMP_MAP_FROM:
 	case GOMP_MAP_FORCE_FROM:
-	case GOMP_MAP_ALWAYS_FROM:
 	  copyfrom = true;
 	  /* Fallthrough.  */