bios: Add/change bios attributes

Added new vtpm bios attributes to the supported list. Also the
attribute name pvm_os_ipl_type is changed to pvm_os_boot_type.

Tested by:
Verified the values using the pldmtool, redfish

1. StringTable o/p:
    "33": "pvm_os_boot_type",
    "42": "pvm_vtpm",

2. AttributeTable o/p:
    {
        "AttributeHandle": 24,
        "AttributeNameHandle": "33(pvm_os_boot_type)",
        "AttributeType": "BIOSEnumeration",
        "NumberOfPossibleValues": 4,
        "PossibleValueStringHandle[0]": "1(A_Mode)",
        "PossibleValueStringHandle[1]": "4(B_Mode)",
        "PossibleValueStringHandle[2]": "5(C_Mode)",
        "PossibleValueStringHandle[3]": "6(D_Mode)",
        "NumberOfDefaultValues": 1,
        "DefaultValueStringHandleIndex[0]": 3,
        "StringHandle": "6(D_Mode)"
    },
    {
        "AttributeHandle": 25,
        "AttributeNameHandle": "42(pvm_vtpm)",
        "AttributeType": "BIOSEnumeration",
        "NumberOfPossibleValues": 2,
        "PossibleValueStringHandle[0]": "8(Disabled)",
        "PossibleValueStringHandle[1]": "9(Enabled)",
        "NumberOfDefaultValues": 1,
        "DefaultValueStringHandleIndex[0]": 0,
        "StringHandle": "8(Disabled)"
    }

3. AttributeValueTable o/p:
    {
        "AttributeHandle": 24,
        "AttributeType": "BIOSEnumeration",
        "NumberOfCurrentValues": 1,
        "CurrentValueStringHandleIndex[0]": "D_Mode"
    },
    {
        "AttributeHandle": 25,
        "AttributeType": "BIOSEnumeration",
        "NumberOfCurrentValues": 1,
        "CurrentValueStringHandleIndex[0]": "Disabled"
    }

4. Redfish GET:
    "pvm_os_boot_type": "D_Mode",
    "pvm_vtpm": "Disabled",

Signed-off-by: Jayashankar Padath <jayashankar.padath@in.ibm.com>
Change-Id: Iefda84ccbde29e1166acb8dabda07f408564cd3f