eal: use correct data type for bitmap slab operations

eal: use correct data type for bitmap slab operations

Currently, slab operations use unsigned long data type for 64-bit slab
related operations. On target 'i686-native-linuxapp-gcc', unsigned long
is 32-bit and thus, slab operations breaks on this target. Changing slab
operations to use unsigned long long for correct functioning on
all targets.

Fixes: de3cfa2c9823 ("sched: initial import")
Fixes: 693f715da45c ("remove extra parentheses in return statement")
Cc: stable@dpdk.org
Signed-off-by: Vivek Sharma <vivek.sharma@caviumnetworks.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>