hwspinlock: remove sirf driver

The CSR SiRF prima2/atlas platforms are getting removed, so this driver
is no longer needed.

Cc: Barry Song <baohua@kernel.org>
Link: https://lore.kernel.org/linux-arm-kernel/20210120124812.2800027-1-arnd@kernel.org/T/


Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210120132537.2285157-1-arnd@kernel.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>