Adjust RGB-to-YUV conversion

Round values rather than truncate them. ITU-R BT.601 indicates that
values should be rounded. Also, correct one coefficient value that
was slightly off.

These errors caused some CTS test failures for the Emulator.

BUG: http://b/31497838
Change-Id: I4c15e02dac266e243d3baf015fd3939877ab930c
(cherry picked from commit 36402501e4d94108db9e35fd3bb03c455d6a1635)