x86: Remove obsolete comment in uapi/e820.h

A comment introduced by this old commit:

  028b785888c5 ("x86 boot: extend some internal memory map arrays to handle larger EFI input")

had to do with some nested preprocessor directives.  The
directives were split into separate files by this commit:

  af170c5061dd ("UAPI: (Scripted) Disintegrate arch/x86/include/asm")

The comment explaining their interaction was retained and is now
present in arch/x86/include/uapi/asm/e820.h.  This comment is no
longer correct, so delete it.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Link: http://lkml.kernel.org/r/1400521824-21040-1-git-send-email-ross.zwisler@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>