Keep track of the set of GSI interrupt types that are currently
enabled by recording the mask value to write (or last written) to
the TYPE_IRQ_MSK register.

Create a new helper function gsi_irq_type_update() to handle
actually writing the register.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>