're done.

A quick test with a 337KiB iwlagn firmware shows the time taken for
request_firmware() going from ~32ms to ~5ms after I apply this patch.

[v2: define PAGE_KERNEL_RO as PAGE_KERNEL where necessary, use min_t()]
[v3: kunmap() takes the struct page *, not the virtual address]

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Tested-by: Sachin Sant <sachinp@in.ibm.com>
Κά