machine:mx8m: Updated preferred gstreamer version 1.18.5

Set the preferred gstreamer version for the i.MX8M devices to
1.18.5.

conf/machine/include/imx8guf.inc

@@ -67,10 +67,10 @@ PREFERRED_PROVIDER:u-boot = "u-boot-imx"
 PREFERRED_PROVIDER_virtual/bootloader = "u-boot-imx"
 PREFERRED_VERSION:u-boot = "2020.04"
 
-PREFERRED_VERSION:gstreamer1.0 = "1.16.imx"
-PREFERRED_VERSION:gstreamer1.0-plugins-base = "1.16.imx"
-PREFERRED_VERSION:gstreamer1.0-plugins-good = "1.16.imx"
-PREFERRED_VERSION:gstreamer1.0-plugins-bad = "1.16.imx"
+PREFERRED_VERSION:gstreamer1.0 = "1.18.5.imx"
+PREFERRED_VERSION:gstreamer1.0-plugins-base = "1.18.5.imx"
+PREFERRED_VERSION:gstreamer1.0-plugins-good = "1.18.5.imx"
+PREFERRED_VERSION:gstreamer1.0-plugins-bad = "1.18.5.imx"
 
 # uImage and zImage build targets are not supported on ARM64.
 # If compressed kernel images are to be used, the bootloader must unpack them.