spmi: Select IRQ_DOMAIN instead of depend on it

IRQ_DOMAIN is a hidden config option, so depending on it doesn't
make any sense. Select the config option because it's required to
compile this driver.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>