MIPS: uprobes: remove set but not used variable 'epc'

Fixes gcc '-Wunused-but-set-variable' warning:

arch/mips/kernel/uprobes.c: In function 'arch_uprobe_pre_xol':
arch/mips/kernel/uprobes.c:115:17: warning: variable 'epc' set but not used [-Wunused-but-set-variable]

It's never used since introduction in
commit 40e084a ("MIPS: Add uprobes support.")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: <ralf@linux-mips.org>
Cc: <jhogan@kernel.org>
Cc: <linux-kernel@vger.kernel.org>
Cc: <linux-mips@vger.kernel.org>

arch/mips/kernel/uprobes.c

@@ -112,9 +112,6 @@ int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs)
 	 */
 	aup->resume_epc = regs->cp0_epc + 4;
 	if (insn_has_delay_slot((union mips_instruction) aup->insn[0])) {
-		unsigned long epc;
-
-		epc = regs->cp0_epc;
 		__compute_return_epc_for_insn(regs,
 			(union mips_instruction) aup->insn[0]);
 		aup->resume_epc = regs->cp0_epc;