When "force" is specified to pmap_invalidate_cache_range(), the given
start address is not required to be page aligned. However, the loop
within pmap_invalidate_cache_range() that performs the actual cache
line invalidations requires that the starting address be truncated to
a multiple of the cache line size. This change corrects an error in
that truncation.

Submitted by: Brett Gutstein <bgutstein@rice.edu>
Reviewed by: kib
MFC after: 1 week