ARM: it8152: add IT8152_LAST_IRQ definition to fix build error

The commit 6ac6b817 (ARM: pxa: encode
IRQ number into .nr_irqs) removed definition of ITE_LAST_IRQ which
caused the following build error:

CC      arch/arm/common/it8152.o
arch/arm/common/it8152.c: In function 'it8152_init_irq':
arch/arm/common/it8152.c:86: error: 'IT8152_LAST_IRQ' undeclared (first use in this function)
arch/arm/common/it8152.c:86: error: (Each undeclared identifier is reported only once
arch/arm/common/it8152.c:86: error: for each function it appears in.)
make[2]: *** [arch/arm/common/it8152.o] Error 1

Defining the IT8152_LAST_IRQ in the arch/arm/include/hardware/it8152.c
fixes the build.

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>