riscv: Fix syscall wrapper for >word-size arguments

riscv: Fix syscall wrapper for >word-size arguments

The current syscall wrapper macros break 64-bit arguments on
rv32 because they only guarantee the first N input registers are
passed to syscalls that accept N arguments. According to the
calling convention, values twice the word size reside in register
pairs and as a result, syscall arguments don't always have a
direct register mapping on rv32.

Instead of using `__MAP(x,__SC_LONG,__VA_ARGS__)` to declare the
type of the `__se(_compat)_sys_*` functions on rv32, change the
function declarations to accept `ulong` arguments and alias them
to the actual syscall implementations, similarly to the existing
macros in include/linux/syscalls.h. This matches previous
behavior and ensures registers are passed to syscalls as-is, no
matter which argument types they expect.

Fixes: 08d0ce30e0e4 ("riscv: Implement syscall wrappers")
Reported-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20240311193143.2981310-2-samitolvanen@google.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>