config: fix CPU and memory parameters on IBM POWER8

config: fix CPU and memory parameters on IBM POWER8

This patch fixes the max logic number and memory channel number settings
on IBM POWER8 platform.
1. The max number of logic cores of a POWER8 processor is 96. Normally,
   there are two sockets on a server. So the max number of logic cores
   are 192. So this parch set CONFIG_RTE_MAX_LCORE to 256.
2. The socket number on POWER8 little endian platform can be larger than 16.
   This patch set CONFIG_RTE_MAX_NUMA_NODES to 32 for POWER8.
3. Currently, the max number of memory channels are hardcoded to 4. However,
   on a POWER8 machine, the max number of memory channels are 8. This patch
   removes the constraint.

Signed-off-by: Chao Zhu <chaozhu@linux.vnet.ibm.com>