grub2: upgrade to 2.02-beta3 (3 years newer than previous)

'100-musl-compat.patch' does not seem to be required anymore.
'210-fix_serial_rtscts.patchi' is superseeded by:
http://git.savannah.gnu.org/cgit/grub.git/commit/?id=bac5d1a64ab4191058a8fd4c05f6b3b339e249e7



Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>