LU-6142 lustre: Remove inappropriate uses of BIT() macro.

LU-6142 lustre: Remove inappropriate uses of BIT() macro.

The BIT() macro exists for identifying a specific bit in a word when
it is being used as a bitmap (or mask for set of flags etc).
While it uses "1 << ...." it is not a general replacement for that
construct and should not be used to simply to raise '2' to some power.

Varous places in lustre and libcfs use BIT() when a size, rather than
a BIT, are required.  Convert these to explicitly use "1 << exponent".

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I41e1e188da4d2e5dff5b2c05cec607c1d104bcfa
Reviewed-on: https://review.whamcloud.com/38373
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>