ENGR00223058 [MX6]Fix build warning

ENGR00223058 [MX6]Fix build warning

Fix below build warning:

arch/arm/mach-mx6/irq.c: In function 'mx6_init_irq':
arch/arm/mach-mx6/irq.c:106: warning: unused variable 'reg'

arch/arm/mach-mx6/clock_mx6sl.c:1807:
	warning: function declaration isn't a prototype
arch/arm/mach-mx6/clock_mx6sl.c:1535:
	warning: 'tzasc1_clk' defined but not used
arch/arm/mach-mx6/clock_mx6sl.c:1576:
	warning: 'mx6per2_clk' defined but not used
arch/arm/mach-mx6/clock_mx6sl.c:1708:
	warning: 'ocram_clk' defined but not used

Signed-off-by: Anson Huang <b20788@freescale.com>