firmware: imx: add missing include of <linux/firmware/imx/sci.h>

firmware: imx: add missing include of <linux/firmware/imx/sci.h>

Include <linux/firmware/imx/sci.h> for the declarations of the
functions exported from this driver. This fixes the following
sparse warnings:

drivers/firmware/imx/imx-scu-irq.c:45:5: warning: symbol 'imx_scu_irq_register_notifier' was not declared. Should it be static?
drivers/firmware/imx/imx-scu-irq.c:52:5: warning: symbol 'imx_scu_irq_unregister_notifier' was not declared. Should it be static?
drivers/firmware/imx/imx-scu-irq.c:97:5: warning: symbol 'imx_scu_irq_group_enable' was not declared. Should it be static?
drivers/firmware/imx/imx-scu-irq.c:130:5: warning: symbol 'imx_scu_enable_general_irq_channel' was not declared. Should it be static?

Signed-off-by: Ben Dooks (Codethink) <ben.dooks@codethink.co.uk>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>