x86/boot/e820: Clean up __e820__update_table() et al

The __e820__update_table() function has various weirdly named variables,
such as 'pbios', 'biosmap' and 'pnr_map' which are pretty confusing
and actively misleading at times.

This weird naming found its way into other functions as well, such as
__append_e820_table() and append_e820_table().

Standardize the naming to make it all much easier to read:

	biosmap  ->  entries
	pbios    ->  entry
	nr_map   ->  nr_entries
        pnr_map  ->  nr_entries
	...

Also clean up the types used: entry indices routinely mixed u32 and int,
standardize on u32 thoughout.

Update the comments as well, while at it.

No change in functionality.

Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Jackson <pj@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>