ARM: LPAE: Move the FSR definitions to separate files

The FSR structure is different with LPAE and this patch moves the
classic MMU specific definition to a separate fsr-2level.c file that is
included in fault.c. It also moves the fsr_fs and FSR bits to the
fault.h file.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>