dmaengine: qcom_hidma: hide MSI handler when unused

The newly added MSI support causes a harmless warning when MSI
is disabled:

drivers/dma/qcom/hidma.c:558:20: error: 'hidma_chirq_handler_msi' defined but not used [-Werror=unused-function]

This adds another #ifdef to match that around the users of the function.

Fixes: 1c0e3e82

 ("dmaengine: qcom_hidma: add MSI support for interrupts")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>