i2c: cmd: Relocate subcommands when MANUAL_RELOC

Subcommands contain pointers to functions which are not updated when
MANUAL_RELOC is enabled. This patch fix it.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>