riscv: use lw when reading int cpu in asm_per_cpu

REG_L is wrong, because thread_info.cpu is 32-bit, not xlen-bit wide.
The struct currently has a hole after cpu, so little endian accesses
seemed fine.

Fixes: be97d0d ("riscv: VMAP_STACK overflow detection thread-safe")
Cc: stable@vger.kernel.org
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Radim Krčmář <rkrcmar@ventanamicro.com>
Link: https://lore.kernel.org/r/20250725165410.2896641-5-rkrcmar@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Author: radimkrcmar

arch/riscv/include/asm/asm.h

@@ -91,7 +91,7 @@
 #endif
 
 .macro asm_per_cpu dst sym tmp
-	REG_L \tmp, TASK_TI_CPU_NUM(tp)
+	lw    \tmp, TASK_TI_CPU_NUM(tp)
 	slli  \tmp, \tmp, PER_CPU_OFFSET_SHIFT
 	la    \dst, __per_cpu_offset
 	add   \dst, \dst, \tmp