backlight: fix module alias prefix for adp8870_bl

This is an i2c driver, not a platform driver, thus use "i2c" prefix for
the module alias.
Signed-off-by: NAxel Lin <axel.lin@gmail.com>
Acked-by: NMichael Hennerich <michael.hennerich@analog.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/backlight/adp8870_bl.c

@@ -1009,4 +1009,4 @@ module_exit(adp8870_exit);
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>");
 MODULE_DESCRIPTION("ADP8870 Backlight driver");
-MODULE_ALIAS("platform:adp8870-backlight");
+MODULE_ALIAS("i2c:adp8870-backlight");