fix data_size and metadata_size types

fix data_size and metadata_size types

The data_size and metadata_size fields in the config struct are declared as
__u32, but should actually be __u64. The current types cause issues in the
argument parsing functions depending on machine architecture and endianness. In
ppc64, using __u32 causes "data size not provided" errors due to the way writes
are being done by argconfig_parse() at src/argconfig.c. Changing the types to
__u64 should fix this behaviour and is in accordance to the CFG_LONG_SUFFIX
flag.

Signed-off-by: Heitor Ricardo Alves de Siqueira <halves@linux.vnet.ibm.com>