x86/build: Remove three unneeded genhdr-y entries

In x86's include/asm/Kbuild three entries are appended to the genhdr-y make
variable:

    genhdr-y += unistd_32.h
    genhdr-y += unistd_64.h
    genhdr-y += unistd_x32.h

The same entries are also appended to that variable in
include/uapi/asm/Kbuild. So commit:

  10b63956 ("UAPI: Plumb the UAPI Kbuilds into the user header installation and checking")

... removed these three entries from include/asm/Kbuild. But, apparently, some
merge conflict resolution re-added them.

The net effect is, in short, that the genhdr-y make variable contains these
file names twice and, as a consequence, that the corresponding headers get
installed twice. And so the build prints:

  INSTALL usr/include/asm/ (65 files)

... while in reality only 62 files are installed in that directory.

Nothing breaks because of all that, but it's a good idea to finally remove
these unneeded entries nevertheless.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1480077707-2837-1-git-send-email-pebolle@tiscali.nlSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/Kbuild

@@ -6,10 +6,6 @@ generated-y += unistd_32_ia32.h
 generated-y += unistd_64_x32.h
 generated-y += xen-hypercalls.h
 
-genhdr-y += unistd_32.h
-genhdr-y += unistd_64.h
-genhdr-y += unistd_x32.h
-
 generic-y += clkdev.h
 generic-y += cputime.h
 generic-y += dma-contiguous.h