target/riscv: Combine set_mode and set_virt functions.

target/riscv: Combine set_mode and set_virt functions.

Combining riscv_cpu_set_virt_enabled() and riscv_cpu_set_mode()
functions. This is to make complete mode change information
available through a single function.

This allows to easily differentiate between HS->VS, VS->HS
and VS->VS transitions when executing state update codes.
For example: One use-case which inspired this change is
to update mode-specific instruction and cycle counters
which requires information of both prev mode and current
mode.

Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240711-smcntrpmf_v7-v8-1-b7c38ae7b263@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>