riscv: bootm: Correct the 1st kernel argument to hart id

riscv: bootm: Correct the 1st kernel argument to hart id

The first argument of Linux kernel is the risc-v core hart id,
from which the kernel is booted from. It is not the mach_id,
which seems to be copied from arm.

While we are here, this also changes the Linux kernel entry
parameters' type to support both 32-bit and 64-bit.

Note the hart id is hardcoded to zero for now, and we should
change to fill in it with the value read from mhartid CSR of
the hart which this routine is currently running on.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Rick Chen <rick@andestech.com>