blackfin: Add <asm/clock.h> to numerous drivers

With d6a320d5 we moved some clock externs out of blackfin_local.h and
into clock.h but now need to include <asm/clock.h> in more drivers to
avoid warnings.

Cc: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Tom Rini <trini@ti.com>