drm/tilcdc: fixing off by one errors found on analyzer

When hooking up to an HDMI analyzer noticed some timings were
off by one.  Referring to the hardware technical reference manual
for the lcd controller some of the timing registers use 0 to
represent 1.  This patch addresses that issue.

Signed-off-by: Darren Etheridge <detheridge@ti.com>
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>