target-arm: Implement MDCR_EL3.TPM and MDCR_EL2.TPM traps

Implement the performance monitor register traps controlled
by MDCR_EL3.TPM and MDCR_EL2.TPM. Most of the performance
registers already have an access function to deal with the
user-enable bit, and the TPM checks can be added there. We
also need a new access function which only implements the
TPM checks for use by the few not-EL0-accessible registers
and by PMUSERENR_EL0 (which is always EL0-readable).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1455892784-11328-3-git-send-email-peter.maydell@linaro.org
Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>
Acked-by: Alistair Francis <alistair.francis@xilinx.com>
