malloc: remove extern declarations of malloc_bin_reloc() in board.c files

malloc: remove extern declarations of malloc_bin_reloc() in board.c files

Declare malloc_bin_reloc() in malloc.h and remove all extern declarations
in various board.c files to get rid of one checkpatch.pl warning.

Signed-off-by: Daniel Schwierzeck <[email protected]>
Cc: Wolfgang Denk <[email protected]>
Cc: Andreas Bießmann <[email protected]>
Cc: Jason Jin <[email protected]>
Cc: Macpaul Lin <[email protected]>
Cc: Daniel Hellstrom <[email protected]>
Acked-by: Andreas Bießmann <[email protected]>