lib: consolidate hang()

Delete all occurrences of hang() and provide a generic function.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
[trini: Modify check around puts() in hang.c slightly]
Signed-off-by: Tom Rini <trini@ti.com>

drivers/mtd/nand/mxc_nand_spl.c

@@ -355,12 +355,3 @@ void nand_boot(void)
 		hang();
 	}
 }
-
-/*
- * Called in case of an exception.
- */
-void hang(void)
-{
-	/* Loop forever */
-	while (1) ;
-}