[media] davinci/vpss: add helper functions for setting hw params

Add vpss helper functions to be used in the main driver for setting
hardware parameters.

Add interface functions to set sync polarity, interrupt completion and
pageframe size in vpss to be used by the main driver.

Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>