arm/einj: adds vendor defined error injection mechanism

This patch introduces a mechanism for performing error injection according to
vendor defined method.

ARM CPU provides Pseudo fault generation system registers for injecting
Correctable(CE), Deferred(DE) errors in CPU. This patch adds functionlities
for user to inject CE, DE.

User gets option to choose component for error injection, type of error,
firmware first or kernel first through debugfs entries.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Signed-off-by: Glen Yeldho <glen.yeldho@arm.com>
Change-Id: I731b475f58e5605ade4e73253431d71492865a73