[media] vpif_cap/disp: Add debug functionality

The following functions are added to the drivers:
    - vpif_g_chip_ident
    - vpif_dbg_g_register
    - vpif_dbg_s_register
    - vpif_log_status

Signed-off-by: Mats Randgaard <mats.randgaard@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Acked-by: Manjunath Hadli <manjunath.hadli@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>