ARM: imx6: build pm-imx6q.c independently of CONFIG_PM

ARM: imx6: build pm-imx6q.c independently of CONFIG_PM

When building a kernel image with only CONFIG_CPU_IDLE but no CONFIG_PM,
we will get the following link error.

  LD      init/built-in.o
arch/arm/mach-imx/built-in.o: In function `imx6q_enter_wait':
platform-spi_imx.c:(.text+0x25c0): undefined reference to `imx6q_set_lpm'
platform-spi_imx.c:(.text+0x25d4): undefined reference to `imx6q_set_lpm'
arch/arm/mach-imx/built-in.o: In function `imx6q_cpuidle_init':
platform-spi_imx.c:(.init.text+0x75d4): undefined reference to `imx6q_set_chicken_bit'
make[1]: *** [vmlinux] Error 1

Since pm-imx6q.c has been a collection of library functions that access
CCM low-power registers used by not only suspend but also cpuidle and
other drivers, let's build pm-imx6q.c independently of CONFIG_PM to fix
above error.

Reported-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: stable@vger.kernel.org
Acked-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>