crush: include header for global symbols

Include the header to pickup the definitions of the global symbols.

Quiets the following sparse warnings:

warning: symbol 'crush_find_rule' was not declared. Should it be static?
warning: symbol 'crush_do_rule' was not declared. Should it be static?

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Sage Weil <sage@newdream.net>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>