We are not checking whether the requested device identifier fits into
the device table memory or not. The function its_create_device()
assumes that enough memory has been allocated for whole DevID space
(reported by ITS_TYPER.Devbits) during the ITS probe() and continues
to initialize ITS hardware.

This assumption is not perfect, sometimes we reduce memory size either
because of its size crossing MAX_ORDER-1 or BASERn max size limit. The
MAPD command fails if 'Device ID' is outside of device table range.

Add a simple validation check to avoid MAPD failures since we are
not handling ITS command errors. This change also helps to return an
error -ENOMEM instead of success to caller.
Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>