bootm: Add board specific OS preboot hook

Add board-specific hook which is executed before the code hands over
control to the OS. This lets the board perform some last-minute clean
ups.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
1 file changed