Additional cleanup for debug boards on H2/P2/H3/H4:  move the init
code that's not board-specific into a new file where it can be easily
shared between all the different boards (avoiding code duplication,
and making it easier to support more devices).  Make H4 use that.

This should be easy to drop in to the OMAP1 boards using these debug
cards; the only difference seems to be that the p2 does an extra reset
of the smc using the fpga (probably all boards could do that, if it's
necessary) and doesn't use the gpio mux or request APIs.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NTony Lindgren <tony@atomide.com>