IB/mthca: Use bitmap_set() when applicable

The 'alloc->table' bitmap has just been allocated, so this is safe to use
the faster and non-atomic 'bitmap_set()' function. There is no need to
hand-write it.

Link: https://lore.kernel.org/r/f1bd33f6ea6c8ad519a222db6e9aa17c55610557.1637785902.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>