Use one helper function to remove copy paste of
aom_quantize_b_c, aom_quantize_b_32x32_c, aom_quantize_b_64x64_c.
And remove redundant av1_quantize_b_c, av1_highbd_quantize_b_c.

BUG=aomedia:442

Change-Id: I3e7923a64a16af223c3e2a42dc27c0f28a9b134b