arm64: zynqmp: Remove description for 8T49N287 and si5382 chips

Based on commit 73d677e9 ("arm64: dts: zynqmp: Remove si5328 device
nodes") also remove description for clock chips which don't have Linux
driver yet.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/7557288230567fa136ba3edc004d5bfe4f4c6590.1623684253.git.michal.simek@xilinx.com