Variable shadowing is, according to the C standard, permitted and valid
behaviour. However, allowing a local variable to take the same name as a
global one can cause confusion and can make refactoring and bug hunting
more difficult.

This patch moves -Wshadow from WARNING2 into the general warning group
so it is always used. It also fixes all warnings that this introduces
by simply renaming the local variable to a new name

Change-Id: I6b71bdce6580c6e58b5e0b41e4704ab0aa38576e
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>