net: airoha: Fix MODULE_LICENSE to match SPDX GPL-2.0-only identifier

Both airoha_eth.c and airoha_npu.c declare SPDX-License-Identifier:
GPL-2.0-only but use MODULE_LICENSE("GPL"), which the kernel module
loader interprets as GPL-2.0+ (any GPL version). This mismatch causes
license compliance tools (FOSSology, ScanCode, etc.) to misidentify
the effective license as more permissive than intended.

Replace MODULE_LICENSE("GPL") with MODULE_LICENSE("GPL v2") to
align with the GPL-2.0-only SPDX identifier. Per include/linux/module.h,
"GPL v2" maps to GPL-2.0-only, matching the source files' declared
license.

Signed-off-by: Wayen <win847@gmail.com>
Link: https://patch.msgid.link/6a2ded59.63d39acb.391892.7632@mx.google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/airoha/airoha_eth.c

@@ -3710,6 +3710,6 @@ static struct platform_driver airoha_driver = {
 };
 module_platform_driver(airoha_driver);
 
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Lorenzo Bianconi <lorenzo@kernel.org>");
 MODULE_DESCRIPTION("Ethernet driver for Airoha SoC");

drivers/net/ethernet/airoha/airoha_npu.c

@@ -826,6 +826,6 @@ MODULE_FIRMWARE(NPU_EN7581_7996_FIRMWARE_DATA);
 MODULE_FIRMWARE(NPU_EN7581_7996_FIRMWARE_RV32);
 MODULE_FIRMWARE(NPU_AN7583_FIRMWARE_DATA);
 MODULE_FIRMWARE(NPU_AN7583_FIRMWARE_RV32);
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Lorenzo Bianconi <lorenzo@kernel.org>");
 MODULE_DESCRIPTION("Airoha Network Processor Unit driver");