Fix typos/incorrect naming in public API's

This commit attempts to fix the pointed typo's &
incorrect naming in the public API's exposed by libpldm.

Resolves https://github.com/openbmc/pldm/issues/30



Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
Change-Id: I5ddab36222ee2a19980fdc507d7c508f3fd18eff