MAINTAINERS: xtensa: drop linux-xtensa@linux-xtensa.org mailing list

The linux-xtensa@linux-xtensa.org mailing list has been bouncing emails
for a few months now. Drop it from the xtensa entries in the MAINTAINERS
file.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

MAINTAINERS

@@ -20647,7 +20647,6 @@ F:	sound/soc/codecs/tscs*.h
 TENSILICA XTENSA PORT (xtensa)
 M:	Chris Zankel <chris@zankel.net>
 M:	Max Filippov <jcmvbkbc@gmail.com>
-L:	linux-xtensa@linux-xtensa.org
 S:	Maintained
 T:	git https://github.com/jcmvbkbc/linux-xtensa.git
 F:	arch/xtensa/
@@ -23039,7 +23038,6 @@ F:	drivers/gpio/gpio-xra1403.c
 
 XTENSA XTFPGA PLATFORM SUPPORT
 M:	Max Filippov <jcmvbkbc@gmail.com>
-L:	linux-xtensa@linux-xtensa.org
 S:	Maintained
 F:	drivers/spi/spi-xtensa-xtfpga.c
 F:	sound/soc/xtensa/xtfpga-i2s.c