staging: r8188eu: Convert header copyright info to SPDX format, part 4

staging: r8188eu: Convert header copyright info to SPDX format, part 4

Before this driver can be incorporated in the drivers/net/wireless tree,
the copyright info in all files must be converted to SPDX notation.
This patch converts the 23 C source files in core/.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Link: https://lore.kernel.org/r/20210729164814.32097-5-Larry.Finger@lwfinger.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>