mmu: default value for slop parameter of linear_map()

slop made page size by default because this is the most frequent case

Signed-off-by: Dmitry Fleytman <dmitry@daynix.com>
acpi: mapping of long tables fixed

Due to incorrect mapping logic ACPI tables longer than PAGE_SIZE
mapped partially and to wrong base address. As a result system crashed
on ACPI tables checksum verification.

Found when running on EC2 HVM instances, the problematic table was:
ACPI: DSDT 0xfc002c40 0321F (v02    Xen      HVM 00000000 INTL 20090220)

Signed-off-by: Dmitry Fleytman <dmitry@daynix.com>