PlatformPkg/FirmwareContextProcessorSpecificLib:Add FirmwareContextProcessorSpecificLib module

Add OpenSBI firmware context processor specific library which
provides interface to create processor specific firmware
context hob data.

Signed-off-by: Abner Chang <abner.chang@hpe.com>
Co-authored-by: Gilbert Chen <gilbert.chen@hpe.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Gilbert Chen <gilbert.chen@hpe.com>