i2c: use usleep_range to wait instead of msleep

according to the docs msleep(1) means wait up 20ms. i2c bus probably
doesn't need to wait that long. Potential performance boost.
optimized LPDDR RAM timings (~10% throughput increase)

Tweaked the device's RAM timings. Benchmarks suggest a 10
percent thorughput improvement (RgBandwidth RAM misc benchmark;
threads: 1. 20 benchmark instances each, best result wins):

       Stock          Tweaked

Copy   1249.9 MB/s -> 1373.0 MB/s --> 9.86 % improvement
Scale  1084.8 MB/s -> 1188.1 MB/s --> 9.52 % improvement
Add    938.4 MB/s  -> 1050.2 MB/s --> 11.91 % improvement
Triad  923.0 MB/s  -> 1043.5 MB/s --> 13.06 % improvement