firmware: smccc: Add the definition for SMCCCv1.2 version/error codes

Add the definition for SMCCC v1.2 version and new error code added.
While at it, also add a note that ARM DEN 0070A is deprecated and is
now merged into the main SMCCC specification(ARM DEN 0028C).

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Etienne Carriere <etienne.carriere@st.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Etienne Carriere <etienne.carriere@st.com>
Link: https://lore.kernel.org/r/20200518091222.27467-4-sudeep.holla@arm.com


Signed-off-by: Will Deacon <will@kernel.org>