"Fix GENMASK macro shift overflow"

Nobody seems to currently use GENMASK() to fill every single last bit
(which is what overflows) in-tree, and gcc would warn about it, so we
have that going for us.  But apparently there are pending changes that
want this.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  bitops: Fix shift overflow in GENMASK macros