libsel4vm: Fault: support 64 bits fault data mask for aarch64

[colorglass]

The function fault_get_data_mask() only produce the mask within 32 bits which meas it can't return a mask like 0xffffffff00000000 with 64 bits seL4_Word. https://github.com/seL4/seL4_projects_libs/blob/eb42051d1217405832165869e034ab8860ed4129/libsel4vm/src/arch/arm/fault.c#L494 Thus for some data structures like GICD_IROUTER of gicv3 which is in 64 bits width, the mask and the related fault function fault_emulate() can't handler the access to the upper 32 bits correctly.