[SCSI] arcmsr: fix iounmap error for Type B adapter

The Type B Adapter teardown does iounmap on pointers subtracted by a
constant offset.  Since the offset is in bytes, we need the pointers to
be of type void * not uint32_t * so the subtraction is done in the
correct units and we iounmap the correct area.

Signed-off-by: Nick Cheng <nick.cheng@areca.com.tw>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>