Blackfin arch: Fix Bug - Kernel does not boot if re-program clocks

On BF561 EBIU_SDGCTL bit 31 controls the SDRAM external data
path width, typically set 0 for a 32-bit bus width. On other
Blackfin derivatives this bit should be set by default.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>