linux/bitmap.h: relax comment on compile-time constant nbits

linux/bitmap.h: relax comment on compile-time constant nbits

It's not clear what's so horrible about emitting a function call to handle
a run-time sized bitmap.  Moreover, gcc also emits a function call for a
compile-time-constant-but-huge nbits, so the comment isn't even accurate.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Rasmus Villemoes <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Yury Norov <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Sudeep Holla <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>