The L2C-220 is different from the L2C-210 and L2C-310 in that every
operation is a background operation: this means we have to use
spinlocks to protect all operations, and we have to wait for every
operation to complete.

Should a second operation be attempted while a previous operation
is in progress, the response will be an imprecise abort.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>