mediatek: mt7629: 6.6: disable LEDS_SMARTRG_LED by default

mediatek: mt7629: 6.6: disable LEDS_SMARTRG_LED by default

When building MT7629 with ALL_KMODS then we get prompted for
LEDS_SMARTRG_LED and this will break CI and in future buildbot compilation.

It depends on I2C so the symbol is hidden until ALL_KMODS is used and I2C
support is available, so disable the LEDS_SMARTRG_LED symbol in 6.6 config
intentionally as is done in the 6.1 mt7629 config.

Signed-off-by: Robert Marko <robimarko@gmail.com>