riscv: Fixup PTR_L for calling exception

Here, PTR_L should be used. The original code was correct, but it
was incorrectly changed to REG_L by commit 1f6d509828d9. Although
this did not affect the current kernel usage, it is a semantic
error that prevents my rv64ilp32 kernel from booting. So, this
patch provides the correction. The reason is improper use of
semantics: this is a pointer load, not a register load.

Fixes: 1f6d509828d9 ("riscv: Improve exception and system call latency")
Signed-off-by: Guo Ren <[email protected]>

Author: guoren83

arch/riscv/kernel/entry.S

@@ -119,7 +119,7 @@ _save_context:
 	add t0, t1, t0
 	/* Check if exception code lies within bounds */
 	bgeu t0, t2, 3f
-	REG_L t1, 0(t0)
+	PTR_L t1, 0(t0)
 2:
 	jalr t1
 	j ret_from_exception