Input: stmfts - fix the MODULE_LICENSE() string

Input: stmfts - fix the MODULE_LICENSE() string

Replace the bogus "GPL v2" with "GPL" as MODULE_LICNSE() string. The
value does not declare the module's exact license, but only lets the
module loader test whether the module is Free Software or not.

See commit bf7fbeeae6db ("module: Cure the MODULE_LICENSE "GPL" vs.
"GPL v2" bogosity") in the details of the issue. The fix is to use
"GPL" for all modules under any variant of the GPL.

Signed-off-by: David Heidelberg <david@ixit.cz>
Link: https://patch.msgid.link/20260409-stmfts5-v4-1-64fe62027db5@ixit.cz
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>