x86/boot/e820: Print gaps in the E820 table

x86/boot/e820: Print gaps in the E820 table

Gaps in the E820 table are not obvious at a glance and can
easily be overlooked.

Print out gaps in the E820 table:

Before:

	BIOS-provided physical RAM map:
	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
After:

	BIOS-provided physical RAM map:
	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
	BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
	BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
	BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
	BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
	BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
	BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved

Also warn about badly ordered E820 table entries:

	BUG: out of order E820 entry!

( this is printed before the entry is printed, so there's no need to
  print any additional data with the warning. )

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20250515120549.2820541-6-mingo@kernel.org