linux-wandboard

[ARM] pgtable: swp pte layout documentation, definitions, and check

Document the layout of our swp PTE entries, adding definitions for
the bit masks/shifts/sizes, and implement MAX_SWAPFILES_CHECK()
such that we fail to build if we are unable to properly encode the
swp type field.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>