hexagon: remove unnecessary prom.h includes

Hexagon does not have a prom.h header, so it is probably broken with
CONFIG_OF enabled. In any case, remove unnecessary prom.h include in
preparation to make prom.h optional.
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Richard Kuo <rkuo@codeaurora.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Cc: linux-hexagon@vger.kernel.org

arch/hexagon/kernel/setup.c

@@ -32,9 +32,6 @@
 #include <asm/hexagon_vm.h>
 #include <asm/vm_mmu.h>
 #include <asm/time.h>
-#ifdef CONFIG_OF
-#include <asm/prom.h>
-#endif
 
 char cmd_line[COMMAND_LINE_SIZE];
 static char default_command_line[COMMAND_LINE_SIZE] __initdata = CONFIG_CMDLINE;