RISC-V: Check for the effective memory privilege mode during PMP checks

RISC-V: Check for the effective memory privilege mode during PMP checks

The current PMP check function checks for env->priv which is not the effective
memory privilege mode.

For example, mstatus.MPRV could be set while executing in M-Mode, and in that
case the privilege mode for the PMP check should be S-Mode rather than M-Mode
(in env->priv) if mstatus.MPP == PRV_S.

This patch passes the effective memory privilege mode to the PMP check.
Functions that call the PMP check should pass the correct memory privilege mode
after reading mstatus' MPRV/MPP or hstatus.SPRV (if Hypervisor mode exists).

Suggested-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Hesham Almatary <Hesham.Almatary@cl.cam.ac.uk>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>