M-profile cores manage interrupts differently from classic cores
and lack the FIQ. Split the interrupt management parts out into
separate headers but keep the endian swapping routines (which are
not profile-dependent) in the common system-arm header.
The initial part of the vector table is common to all Cortex-M
CPUs and is intended to be included by the target linker script,
with the vendor-specific part of the vector table appended to it.
Change-Id: Ib2ad5b9dc41db27940e39033cfef4308923db66d
