media: atomisp: cleanup isys_irq headers
Don't need to declare those functions with extern:
drivers/staging/media/atomisp/pci/css_2401_system/host/isys_irq_private.h:51:35: warning: function 'isys_irqc_state_dump' with external linkage has definition
drivers/staging/media/atomisp/pci/css_2401_system/host/isys_irq_private.h:68:35: warning: function 'isys_irqc_reg_store' with external linkage has definition
drivers/staging/media/atomisp/pci/css_2401_system/host/isys_irq_private.h:85:39: warning: function 'isys_irqc_reg_load' with external linkage has definition
drivers/staging/media/atomisp/pci/css_2401_system/host/isys_irq.c:31:35: warning: function 'isys_irqc_status_enable' with external linkage has definition
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>