riscv: uaccess: Allow the last potential unrolled copy

When the dst buffer pointer points to the last accessible aligned addr, we
could still run another iteration of unrolled copy.

Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240313103334.4036554-1-xiao.w.wang@intel.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: XiaoWang1772

arch/riscv/lib/uaccess.S

@@ -103,7 +103,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
 	fixup REG_S   t4,  7*SZREG(a0), 10f
 	addi	a0, a0, 8*SZREG
 	addi	a1, a1, 8*SZREG
-	bltu	a0, t0, 2b
+	bleu	a0, t0, 2b
 
 	addi	t0, t0, 8*SZREG /* revert to original value */
 	j	.Lbyte_copy_tail