ibacm: define prov_lib_path as a char array

ibacm: define prov_lib_path as a char array

This patch fixes a segfault error when the option file defines the provider
lib path. The variable prov_lib_path should be a buffer (char array) instead
of a char pointer. This allows a string to be copied into it during option
parsing.

Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>