ARM: 7077/1: LPAE: Use a mask for physical addresses in page table entries

With LPAE, the physical address mask is 40-bit while the page table
entry is 64-bit. This patch introduces PHYS_MASK for the 2-level page
table format, defined as ~0UL.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>