imx8: Replace PLAT_IMX8* with automatic PLAT_imx8*

Platform defines are already provided by the build system so let's not
duplicate them.

Change-Id: Icf1ea76c3c3213e27b447c95e2b22b961fa7693e
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
diff --git a/plat/imx/common/include/imx_sip_svc.h b/plat/imx/common/include/imx_sip_svc.h
index f532840..5898f7a 100644
--- a/plat/imx/common/include/imx_sip_svc.h
+++ b/plat/imx/common/include/imx_sip_svc.h
@@ -33,7 +33,7 @@
 			 u_register_t x2, u_register_t x3);
 #endif
 
-#if (defined(PLAT_IMX8QM) || defined(PLAT_IMX8QX))
+#if (defined(PLAT_imx8qm) || defined(PLAT_imx8qx))
 int imx_cpufreq_handler(uint32_t smc_fid, u_register_t x1,
 			u_register_t x2, u_register_t x3);
 int imx_srtc_handler(uint32_t smc_fid, void *handle, u_register_t x1,