Fix build warning

beagle.c:532: warning: initialization from incompatible pointer type

Signed-off-by: Dirk Behme <dirk.behme@googlemail.com>
CC: Jason Kridner <jkridner@beagleboard.org>
CC: Koen Kooi <koen@dominion.thruhere.net>
CC: Joel A Fernandes <agnel.joel@gmail.com>
Cc: Greg Turner <gregturner@ti.com>
CC: Sandeep Paulraj <s-paulraj@ti.com>
Acked-by: Jason Kridner <jkridner@beagleboard.org>