efi/esrt: Use efi_mem_reserve() and avoid a kmalloc()

efi/esrt: Use efi_mem_reserve() and avoid a kmalloc()

We can use the new efi_mem_reserve() API to mark the ESRT table as
reserved forever and save ourselves the trouble of copying the data
out into a kmalloc buffer.

The added advantage is that now the ESRT driver will work across
kexec reboot.

Tested-by: Dave Young <[email protected]> [kexec/kdump]
Tested-by: Ard Biesheuvel <[email protected]> [arm]
Acked-by: Ard Biesheuvel <[email protected]>
Cc: Leif Lindholm <[email protected]>
Cc: Peter Jones <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>