LU-6142 libcfs: use BIT() macro where appropriate

LU-6142 libcfs: use BIT() macro where appropriate

When accessing a bit in a bitmap/mask/flags-word it can be more
readable to use BIT(num) rather than "1 << num".

This patch makes that change to various places in libcfs.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I5e945358d2385599f8fe6f1ddff310efe17b589f
Reviewed-on: https://review.whamcloud.com/38374
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>