efi: rt-wrapper: Add missing include

commit 18bba184 upstream.

Add the missing #include of asm/assembler.h, which is where the ldr_l
macro is defined.

Fixes: ff7a1679 ("arm64: efi: Execute runtime services from a dedicated stack")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Lee Jones <lee@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>