ARM: socfpga: Pull PL310 clearing into common code

ARM: socfpga: Pull PL310 clearing into common code

Pull the PL310 clearing code into common code, so it can be reused
by Arria10.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Chin Liang See <[email protected]>
Cc: Dalon Westergreen <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Simon Goldschmidt <[email protected]>
Cc: Tien Fong Chee <[email protected]>