efi/libstub: measure initrd to PCR9 independent of source

Currently the initrd is only measured if it can be loaded using the
INITRD_MEDIA_GUID, if we are loading it from a path provided via the
command line it is never measured. Lets move the check down a couple
lines so the measurement happens independent of the source.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>