soc: imx: gpc: build gpc only if hardware has gpc

Add CONFIG_HAVE_IMX_GPC to goal definition of gpc.o,
to avoid building it for hardware that does not need it.
Signed-off-by: Marc Ohlf <ohlf@mkt-sys.de>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/soc/imx/Makefile

-obj-y += gpc.o
+obj-$(CONFIG_HAVE_IMX_GPC) += gpc.o
 obj-$(CONFIG_IMX7_PM_DOMAINS) += gpcv2.o