riscv: __asm_copy_to-from_user: Fix: fail on RV32

Had a bug when converting bytes to bits when the cpu was rv32.

The a3 contains the number of bytes and multiple of 8
would be the bits. The LGREG is holding 2 for RV32 and 3 for
RV32, so to achieve multiple of 8 it must always be constant 3.
The 2 was mistakenly used for rv32.
Signed-off-by: NAkira Tsukamoto <akira.tsukamoto@gmail.com>
Fixes: ca6eaaa2 ("riscv: __asm_copy_to-from_user: Optimize unaligned memory access and pipeline stall")
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/lib/uaccess.S

@@ -125,7 +125,7 @@ ENTRY(__asm_copy_from_user)
 	 * t3 - prev shift
 	 * t4 - current shift
 	 */
-	slli	t3, a3, LGREG
+	slli	t3, a3, 3 /* converting bytes in a3 to bits */
 	li	a5, SZREG*8
 	sub	t4, a5, t3