radeon: move bof.[ch] out of libdrm_radeon

The functions(files) are used if one explicitly modifies radeon_cs_gem.c
by setting CS_BOF_DUMP to 1. As bof.[ch] is used (copied) to other
out-of-tree projects, keep them around in the distribution tarball.

Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>