1) Rework event handling and static registration mechanism. No target-
specific code in mc13783 driver. GPIO event driver interfaces more
cleanly.
2) Somewhat related - enable thread priority for bootloader which is
desireable here (ffs is used for GPIO event enabling anyway and that
goes along with priority).
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17593 a1c6a512-1295-4272-9138-f99709370657
