c6x: run do_notify_resume with interrupts enabled

C6x was mistakenly running do_notify_resume with interrupts disabled.
This would triggerlead to a warning in local_bh_enable() because interrupts
were disabled:

------------[ cut here ]------------
WARNING: at /es/linux/linux-next/kernel/softirq.c:160 local_bh_enable+0x5c/0x10c()
Modules linked in:

             e02f384d e002cda8 e02f3469 e02f384d 000000a0 e00363fc e01cce58 e5005c00
             e0327986 00000000 e63c0aec 00000164 e00363fc 00000000 fffffffe e5005c00
             e61fde00 e0268184 00000134 e01c91dc 00000001 fffffffe 00000000 10000100
             e01c80e4 e5005c00 00000000 00000000 00000000 e63c0aec e526ce00 10000100
             e628f920 e63c0a88 e6010410 e6449750 e5005c20 00000000 00000000 e63c0a80
             e5005c20 e01c8590 e63c0a80 e5005c20 e63c0aec e00a0554 e009c758 e639e860
 irq_spurious_proc_fops+0x6ad/0x3438
 warn_slowpath_common+0x8c/0xb8
 irq_spurious_proc_fops+0x2c9/0x3438
 irq_spurious_proc_fops+0x6ad/0x3438
 local_bh_enable+0x5c/0x10c
 sk_alloc+0x34/0xa4
 local_bh_enable+0x5c/0x10c
 unix_release_sock+0x5c/0x2a0
 sys_connect+0x94/0xd4
 sock_release+0x38/0x104
 sock_close+0x3c/0x54
 __fput+0x154/0x2ec
 filp_close+0xc0/0xe4
 task_work_run+0xdc/0x12c
 sys_close+0x2c/0x74
 resume_userspace+0x0/0x30
---[ end trace a70cbd610ae1f6b4 ]---

This patch enables interrupts before calling do_notify_resume().
Signed-off-by: Mark Salter <msalter@redhat.com>

arch/c6x/kernel/entry.S

@@ -277,6 +277,8 @@ work_rescheduled:
  [A1]	BNOP	.S1	work_resched,5
 
 work_notifysig:
+	;; enable interrupts for do_notify_resume()
+	UNMASK_INT B2
 	B	.S2	do_notify_resume
 	LDW	.D2T1	*+SP(REGS__END+8),A6 ; syscall flag
 	ADDKPC	.S2	resume_userspace,B3,1