malloc: make malloc_bin_reloc static

On architectures where manual relocation
is needed, the 'malloc_bin_reloc' function
must be called after 'mem_malloc_init'.

Make the 'malloc_bin_reloc' function static
and call it directly from 'mem_malloc_init'
instead of calling that from board_init_{r,f}
functions of the affected architectures.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Andreas Bießmann <andreas.devel@gmail.com>
Cc: Jason Jin <Jason.jin@freescale.com>
Cc: Macpaul Lin <macpaul@andestech.com>
Cc: Daniel Hellstrom <daniel@gaisler.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>