modutils-initscripts: Change license PD -> MIT

modutils-initscripts: Change license PD -> MIT

The file was originally added to OE here:
https://git.openembedded.org/openembedded/commit/modutils/files/modutils.sh?id=3b3989442075d0a4c6c32cb187de17d87bf65fbd

and the license added here as "PD":
https://git.openembedded.org/openembedded/commit/modutils/modutils-initscripts.oe?id=4f7d2b1b63d166e5de146d71e5c942419424446e

As "Public Domain", we can re-license it to MIT, which fits in with the rest of
our metadata and has an SPDX identifier, so lets do that and try and keep our
licenses simpler.

This also them removes the need for a weird license patch in SRC_URI.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>