beagleboneblack: trim down linux config further

This removes quite a few more modules and features that were
being built, but not used. It also builds the pruss driver
into the kernel rather than leaving it as a module as that
seems easier when dealing with the PRU.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
am335x-pru-package: fix PRU example file path

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>