pldm: Migrate off deprecated libpldm BIOS table entry encoding APIs

libpldm has deprecated the affected APIs. Prefer using their `*_check()`
variants as these return an error code rather than prevent misbehaviour
with assert().

1. pldm_bios_table_attr_entry_integer_encode()
2. pldm_bios_table_attr_value_entry_encode_enum()
3. pldm_bios_table_attr_value_entry_encode_string()
4. pldm_bios_table_attr_value_entry_encode_integer()

Tested: Successfully booted a p10bmc host, dumped each of the BIOS
        tables with pldmtool without issue

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I823b24884e518f8c53fd153b3bc30569595ecd86