alpha: use generic current.h

Given that the arch does not add its own implementations, simply use the
asm-generic/current.h (generic-y) header instead of duplicating code.

Link: http://lkml.kernel.org/r/1485992878-4780-2-git-send-email-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/include/asm/Kbuild

@@ -9,3 +9,4 @@ generic-y += mm-arch-hooks.h
 generic-y += preempt.h
 generic-y += sections.h
 generic-y += trace_clock.h
+generic-y += current.h

arch/alpha/include/asm/current.h

@@ -1,9 +0,0 @@
-#ifndef _ALPHA_CURRENT_H
-#define _ALPHA_CURRENT_H
-
-#include <linux/thread_info.h>
-
-#define get_current()	(current_thread_info()->task)
-#define current		get_current()
-
-#endif /* _ALPHA_CURRENT_H */