ANDROID: GKI: genirq: Export symbols to compile irqchip drivers as modules

We want to allow compiling irqchip drivers as modules. So export the
necessary symbols.

Bug: 148105066
Change-Id: Id3de4b8451bed1af9b0afeb5863493697730acb6
Signed-off-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>
(cherry picked from commit cfc69e9b2fe82a46addfcb1912bd642456548baa)