ARM: bcm2835_defconfig: disable DEBUG_LL

This way the kernel works on both RPi0/1 and RPi2 even with earlyprintk
in the kernel cmdline; the two hardware platforms use different physical
addresses for peripherals, so the same DEBUG_LL configuration won't work
on both. If someone needs DEBUG_LL support, they can enable it locally.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Eric Anholt <eric@anholt.net>