efi/x86: Get full memory map in allocate_e820()

Currently allocate_e820() is only interested in the size of map and size
of memory descriptor to determine how many e820 entries the kernel
needs.

UEFI Specification version 2.9 introduces a new memory type --
unaccepted memory. To track unaccepted memory, the kernel needs to
allocate a bitmap. The size of the bitmap is dependent on the maximum
physical address present in the system. A full memory map is required to
find the maximum address.

Modify allocate_e820() to get a full memory map.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20230606142637.5171-3-kirill.shutemov@linux.intel.com