nitro_enclaves: Update copyright statement to include 2021

nitro_enclaves: Update copyright statement to include 2021

Update the copyright statement to include 2021, as a change has been
made over this year.

Check commit d874742f6a73 ("nitro_enclaves: Set Bus Master for the NE
PCI device") for the codebase update from this file (ne_pci_dev.c).

Reviewed-by: George-Aurelian Popescu <popegeo@amazon.com>
Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
Link: https://lore.kernel.org/r/20210827154930.40608-5-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>