techpack: camera: Remove unused dw9784 functions

Fixes:
ld.lld: warning: techpack/camera/drivers/cam_sensor_module/cam_ois/
    dw9784_ois.c:1177:0: stack frame size (41120) exceeds limit (2048)
    in function 'dw9784_fw_read'
ld.lld: warning: techpack/camera/drivers/cam_sensor_module/cam_ois/
    dw9784_ois.c:1202:0: stack frame size (2720) exceeds limit (2048)
    in function 'dw9784_flash_if_ram_read'

Change-Id: I078e3702e3e6def12d7d9c03cc1d2a531c3302c2