rtc: stmp3xxx: update contact email

The 'pengutronix' address is defunct for years. Use the proper contact
address.

Signed-off-by: Wolfram Sang <wsa@kernel.org>
Link: https://lore.kernel.org/r/20200502142704.19308-1-wsa@kernel.org


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>