staging: lustre: libcfs: Remove bitmap.h file

The functions in the bitmap.h header file are not being used by
any source file in the lustre driver.

Unless there are any objections, please remove the bitmap.h
header file as it contains unused code in the kernel.

Signed-off-by: Lisa Nguyen <lisa@xenapiadmin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>