init: increase boot speed

Adapted from https://github.com/LegacyXperia/android_device_semc_msm7x30-common/commit/bf6a68f34a6980a690c1503c600970444077bbb6

From original commit:

 * Use the noop I/O scheduler while booting.
   This dramatically improves the bootup time. Noop is ideal
   for high-throughput applications on non-rotating storage, but
   is not designed for interactive usage like ROW or CFQ.

Change-Id: I1f0dd35afbc5c4c7533028fe7d00bb178728b50a