Pull up following revision(s) (requested by riastradh in ticket #1001):
sys/external/bsd/drm2/include/linux/bitops.h: revision 1.10
sys/external/bsd/drm2/include/linux/bitops.h: revision 1.11
Fix indexing convention of Linux __ffs/__ffs64 shims.
They reject zero input, and yield zero-based indexing, unlike our
ffs/ffs64, which return zero for zero and yield one-based indexing.
May let nouveau make a little more progress toward booting!
Found by mrg@.
Fix comment in previous.

(riz)