ARM: socfpga: Fully unmap the FPGA bridges from L3 space

ARM: socfpga: Fully unmap the FPGA bridges from L3 space

Instead of just putting the bridges into reset, fully remove the bridges
from the L3 main bridge space when disabling them by clearing bits in
NIC-301 remap register. Moreover, only touch the 3 LSbits in brgmodrst
register as the rest of the bits are undefined.

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