Removes very complex boot-time generation of page tables
with a much simpler runtime generation of them at bootup.
For those x86 boards that enable the MMU in the defconfig,
set the number of page pool pages appropriately.
The MMU_RUNTIME_* flags have been removed. They were an
artifact of the old page table generation and did not
correspond to any hardware state.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>