spi: altera: fix size mismatch on 64 bit processors

The spi-altera driver was originally written with a 32
bit processor, where sizeof(unsigned long) is 4.  On a
64 bit processor sizeof(unsigned long) is 8.  Change the structure
member to u32 to match the actual size of the control
register.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Reviewed-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/1592531021-11412-4-git-send-email-yilun.xu@intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>