Platform/ARM: Add base Sram Ecc error handling driver

Support added for handling 1-bit CE that are detected by Sram Ecc.

The driver implements the HEST error source descriptor protocol in order
to publish the GHESv2 type error source descriptor for 1-bit Sram
errors. The GHESv2 error source descriptor that is published is of type
'Memory Type Error'.

The driver registers a MMI handler for handling 1-bit CE errors. On
error event, the TF-A calls into secure partition with error info like
whether the error occured on secure or non secure Sram. The MMI handler
populates Memory Error Section information structure and returns.

Signed-off-by: Omkar Anand Kulkarni <omkar.kulkarni@arm.com>
Change-Id: I44b4209eac05f0c35146d40903d3ab47fac21457