kern/efi/mm: Detect calls to grub_efi_drop_alloc() with wrong page counts

kern/efi/mm: Detect calls to grub_efi_drop_alloc() with wrong page counts

Silently keeping entries in the list if the address matches, but the
page count doesn't is a bad idea, and can lead to double frees.

grub_efi_free_pages() have already freed parts of this block by this
point, and thus keeping the whole block in the list and freeing it again
at exit can lead to double frees.

Signed-off-by: Mate Kukri <mate.kukri@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>