bitmap.h: fix kernel-doc warning and typo

Fix kernel-doc warning in <linux/bitmap.h>:

  include/linux/bitmap.h:341: warning: Function parameter or member 'nbits' not described in 'bitmap_or_equal'

Also fix small typo (bitnaps).

Link: http://lkml.kernel.org/r/0729ea7a-2c0d-b2c5-7dd3-3629ee0803e2@infradead.org
Fixes: b9fa6442f7 ("cpumask: Implement cpumask_or_equal()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/bitmap.h

@@ -326,10 +326,11 @@ static inline int bitmap_equal(const unsigned long *src1,
 }
 
 /**
- * bitmap_or_equal - Check whether the or of two bitnaps is equal to a third
+ * bitmap_or_equal - Check whether the or of two bitmaps is equal to a third
  * @src1:	Pointer to bitmap 1
  * @src2:	Pointer to bitmap 2 will be or'ed with bitmap 1
  * @src3:	Pointer to bitmap 3. Compare to the result of *@src1 | *@src2
+ * @nbits:	number of bits in each of these bitmaps
  *
  * Returns: True if (*@src1 | *@src2) == *@src3, false otherwise
  */