[MIPS] Let gcc align 'struct pt_regs' on 8 bytes boundary

The stack pointer in MIPS/gcc should always 8 bytes aligned on
entry to any routines. Therefore pt_regs structure must be
aligned to 8-byte boundary too.

Instead of creating dummy fields to achieve this alignment, this
patch let gcc doing it. Therefore 'smtc_pad' field can be safely
removed.
Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/ptrace.h

@@ -44,9 +44,8 @@ struct pt_regs {
 	unsigned long cp0_epc;
 #ifdef CONFIG_MIPS_MT_SMTC
 	unsigned long cp0_tcstatus;
-	unsigned long smtc_pad;
 #endif /* CONFIG_MIPS_MT_SMTC */
-};
+} __attribute__ ((aligned (8)));
 
 /* Arbitrarily choose the same ptrace numbers as used by the Sparc code. */
 #define PTRACE_GETREGS		12