mt76: use SPDX header file comment style

header files should use '/* SPDX ... */
Change from c file comment syle to header style
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7615/sdio.h

-// SPDX-License-Identifier: ISC
+/* SPDX-License-Identifier: ISC */
 /* Copyright (C) 2020 MediaTek Inc.
  *
  * Author: Sean Wang <sean.wang@mediatek.com>

drivers/net/wireless/mediatek/mt76/mt7915/testmode.h

-// SPDX-License-Identifier: ISC
+/* SPDX-License-Identifier: ISC */
 /* Copyright (C) 2020 MediaTek Inc. */
 
 #ifndef __MT7915_TESTMODE_H