Silicon/RISC-V: Update old SMBIOS struct filed name

The "ProcessorManufacture" field of SMBIOS_TABLE_TYPE4 was recently
renamed to "ProcessorManufacturer". This is causing a compilation
error for RISC-V/SiFive builds. Switch to the new name.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Abner Chang <abner.chang@hpe.com>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Cc: Gilbert Chen <gilbert.chen@hpe.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
Reviewed-by: Abner Chang <abner.chang@hpe.com>