oem-ibm : Support New record to the backplane vpd

This commit is to support a new VPD record called PSPD that contains
few keywords called #D and VM. Since these keywords are typically
larger in size (4K bytes) than what is managed by PLDM, we are adding
a file into which these keywords will be extracted. This keyword file
is transferred to the HB PLDM layer with a readFileByType request
from HB.

This also includes transfer of PSPD record data via PLDM with
offset included.

Tested by using pldmtool to send read request command to PLDM

Change-Id: Iba814a802cbbd2c2d641ee5a4c81919c3b8bdf20
Signed-off-by: Varsha Kaverappa <vkaverap@in.ibm.com>