We currently reset and enable the SMMU before the device has finished
being probed, so if we fail later on (for example, because we couldn't
request a global irq successfully) then we will leave the device in an
active state.

This patch delays the reset and enabling of the SMMU hardware until
probing has completed.

Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>