wl12xx/sdio_test.c: fix build breakage from WL127X_FW_NAME change

Commit c302b2c9 ("wl12xx: Use a single
fw for both STA and AP roles") changed the name of the firmware name
definition, breaking the build of wl12xx/sdio_test.c.

Signed-off-by: John W. Linville <linville@tuxdriver.com>