ARM: 7155/1: arch.h: Declare 'pt_regs' locally

Fix the following warning when building imx_v4_v5_defconfig target:

  CC      arch/arm/mach-imx/mach-imx27ipcam.o
In file included from arch/arm/mach-imx/mach-imx27ipcam.c:18:
/home/fabio/linus/linux-2.6/arch/arm/include/asm/mach/arch.h:47: warning: 'struct pt_regs' declared inside parameter list
/home/fabio/linus/linux-2.6/arch/arm/include/asm/mach/arch.h:47: warning: its scope is only this definition or declaration, which is probably not what you want
arch/arm/mach-imx/mach-imx27ipcam.c:78: warning: initialization from incompatible pointer type

Declare 'struct pt_regs' locally.

Cc: Eric Miao <eric.miao@canonical.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>