Fix a potential crash due to unbound array access

It was reported that, there is an inaccurate check in host_pdr_handler
code that could lead to an unbound access of an array resulting in pldm
crash. This commit aims at fixing it.

Resolves openbmc/pldm/#36

Change-Id: I1bba25f5b1cad55a30ce956f83b8c15b93149219
Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>