dt-bindings: nvmem: Use soc-nvmem node name instead of nvmem

dt-bindings: nvmem: Use soc-nvmem node name instead of nvmem

Based on commit d8764d347bd7 ("dt-bindings: firmware: xilinx: Describe
soc-nvmem subnode") soc-nvmem should be used instead of simple nvmem that's
why also update example to have it described correctly everywhere.

Fixes: c7f99cd8fb6b ("dt-bindings: nvmem: Convert xlnx,zynqmp-nvmem.txt to yaml")
Cc: stable <stable@kernel.org>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240902142510.71096-4-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>