include/linux/res_counter.h needs errno.h

include/linux/res_counter.h needs errno.h

alpha allmodconfig:

  In file included from mm/memcontrol.c:28:
  include/linux/res_counter.h: In function 'res_counter_set_limit':
  include/linux/res_counter.h:203: error: 'EBUSY' undeclared (first use in this function)
  include/linux/res_counter.h:203: error: (Each undeclared identifier is reported only once
  include/linux/res_counter.h:203: error: for each function it appears in.)

Cc: Kamezawa Hiroyuki <[email protected]>
Cc: Glauber Costa <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>