arm: socfpga: Zap spl.h and ad-hoc related syms

arm: socfpga: Zap spl.h and ad-hoc related syms

Switch to the common spl.h file and zap the arch/spl.h . Since the arch/spl.h
contained various ad-hoc symbols, zap those symbols as well and rework the
board configuration a little so it doesn't depend on them.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Chin Liang See <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Vince Bridgers <[email protected]>
Cc: Albert Aribaud <[email protected]>
Acked-by: Pavel Machek <[email protected]>