MAINTAINERS: Add entry for BD71828 charger

Add an entry for BD71828 charger driver.

Signed-off-by: Andreas Kemnade <[e-mail]>
Suggested-by: Matti Vaittinen <[e-mail]>
Reviewed-by: Matti Vaittinen <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

MAINTAINERS

···
 S:	Odd Fixes
 F:	drivers/tty/serial/rp2.*
 
+ROHM BD71828 CHARGER
+M:	Andreas Kemnade <[e-mail]>
+M:	Matti Vaittinen <[e-mail]>
+S:	Maintained
+F:	drivers/power/supply/bd71828-charger.c
+
 ROHM BD79703 DAC
 M:	Matti Vaittinen <[e-mail]>
 S:	Supported