x86/boot: Remove unnecessary #include <generated/utsrelease.h>

The <generated/utsrelease.h> defines UTS_RELEASE, but I do not
see any reference to it in arch/x86/boot/header.S.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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/1505921232-8960-1-git-send-email-yamada.masahiro@socionext.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>