drivers:staging:silicom Fixed extern warnings reported by checkpatch

1) Deleted  bp_proc_create() declaration from bp_mod.h,
because it is declared as static in bpctl_mod.c and not used anywhere.

2) checkpatch warns about
     WARNING: externs should be avoided in .c files

because we have function declarations in bptcl_mod.c,These
functions are not used anywhere else so made them static.

Signed-off-by: Surendra Patil <surendra.tux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>