arm: dts: Add xlnx prefix to GEM compatible string

cdns,zynq/zynqmp were recentle deprecated in Linux in favour of xlnx
prefix. Add this new compatible string and retain the existing string for
compatibility with uboot drivers.

Signed-off-by: Harini Katakam <harini.katakam@amd.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/a38b1b55132fc026cc09224dba61e42fd03b1a36.1661259558.git.michal.simek@amd.com
2 files changed