riscv: Move cast inside kernel_mapping_[pv]a_to_[vp]a

Before commit 44c92257 ("RISC-V: enable XIP"), these macros cast
their argument to unsigned long. That commit moved the cast after an
assignment to an unsigned long variable, rendering it ineffectual.
Move the cast back, so we can remove the cast at each call site.

Reviewed-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20221126060920.65009-2-samuel@sholland.org


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>