DESC
(undescribed patch)
EDESC
This fixes a bug spotted by the iomem tester in the test suite.  mmapper
returns -EFAULT if the mmap length is greater than the iomem region size.
If that size is less than one page, then mmap can never succeed because
the minimum map length is one page.  This fixes that by rounding the iomem
file size up to the nearest page.