mm, sl[aou]b: Use a common mutex definition

mm, sl[aou]b: Use a common mutex definition

Use the mutex definition from SLAB and make it the common way to take a sleeping lock.

This has the effect of using a mutex instead of a rw semaphore for SLUB.

SLOB gains the use of a mutex for kmem_cache_create serialization.
Not needed now but SLOB may acquire some more features later (like slabinfo
/ sysfs support) through the expansion of the common code that will
need this.

Reviewed-by: Glauber Costa <[email protected]>
Reviewed-by: Joonsoo Kim <[email protected]>
Signed-off-by: Christoph Lameter <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>