Backup: speedup

The touchpad firmware should not actually requires at least 1 ms,
not 10 ms a 10 msec pause between writing bootloader 'read' command and a
subsequent data buffer read.

Also, instead of reading the command header (first 16 registers) time,
only read the data registers (starting with byte 16).

Combined, this reduces backup time from ~45 seconds to ~10 seconds.
Eliminating the msleep(1) could speed up by almost another factor of 2,
down to ~5.5 seconds.

TEST=backup 100 times, no false reads

Change-Id: I3344b38af0614ba233d8e7072bc0c9587a13a001
1 file changed