RISC-V: Update AT_VECTOR_SIZE_ARCH for new AT_MINSIGSTKSZ

"riscv: signal: Report signal frame size to userspace via auxv" (e92f469b)
has added new constant AT_MINSIGSTKSZ but failed to increment the size of
auxv, keeping AT_VECTOR_SIZE_ARCH at 9.
This fix correctly increments AT_VECTOR_SIZE_ARCH to 10, following the
approach in the commit 94b07c1f ("arm64: signal: Report signal frame size
to userspace via auxv").

Link: https://lore.kernel.org/r/73883406.20231215232720@torrio.net
Link: https://lore.kernel.org/all/20240102133617.3649-1-victor@torrio.net/


Reported-by: Ivan Komarov <ivan.komarov@dfyz.info>
Closes: https://lore.kernel.org/linux-riscv/CY3Z02NYV1C4.11BLB9PLVW9G1@fedora/


Fixes: e92f469b ("riscv: signal: Report signal frame size to userspace via auxv")
Signed-off-by: Victor Isaev <isv@google.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>