ARM: dts: msm: adjust r61318 r63417 panel min fps to 50 for 8929 platform

r61318 and r63417 panel have flicker issue when fps less than
50 fps as panel do not support it. Modify the min fps to 50 to
avoid this issue.

Change-Id: I71cb7a707ff4832b9d48462d843bca7f40fbd47d
Signed-off-by: Shuo Yan <shuoy@codeaurora.org>