drivers/char/amiserial.c: add missing local_irq_restore

rs_init() is failing to restore interrupts on two error paths, and is
incorrectly calling tty_unregister_driver() with local interrupts
disabled.

Fix these things by disabling interrupts later, after the reauest_irq()
calls.

A simplified version of the semantic patch that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@r exists@
expression E1;
identifier f;
@@

f (...) { <+...
* local_irq_save (E1,...);
... when != E1
* return ...;
...+> }
// </smpl>

[akpm@linux-foundation.org: reimplement the fix]
Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/amiserial.c

@@ -2021,8 +2021,6 @@ static int __init rs_init(void)
 	state->baud_base = amiga_colorclock;
 	state->xmit_fifo_size = 1;
 
-	local_irq_save(flags);
-
 	/* set ISRs, and then disable the rx interrupts */
 	error = request_irq(IRQ_AMIGA_TBE, ser_tx_int, 0, "serial TX", state);
 	if (error)
@@ -2033,6 +2031,8 @@ static int __init rs_init(void)
 	if (error)
 		goto fail_free_irq;
 
+	local_irq_save(flags);
+
 	/* turn off Rx and Tx interrupts */
 	custom.intena = IF_RBF | IF_TBE;
 	mb();