plugins/cache: make L2 emulation optional through args

plugins/cache: make L2 emulation optional through args

By default L2 is not enabled and is enabled by either using the
newly-introduced "l2" boolean argument, or by setting any of the L2
cache parameters using args. On specifying "l2=on", the default cache
configuration is used.

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210810134844.166490-5-ma.mandourr@gmail.com>
Message-Id: <20211026102234.3961636-17-alex.bennee@linaro.org>