target/riscv: Drop priv level check in mseccfg predicate()

target/riscv: Drop priv level check in mseccfg predicate()

riscv_csrrw_check() already does the generic privilege level check
hence there is no need to do the specific M-mode access check in
the mseccfg predicate().

With this change debugger can access the mseccfg CSR anytime.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Message-ID: <20230228104035.1879882-18-bmeng@tinylab.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>