board_r: move initr_watchdog to be called after initr_serial

The initr_watchdog is currently placed before initr_serial. The
initr_watchdog calls printf and printf finally calls ops->putc of a serial
driver.

However, gd->cur_serial_dev points to a udevice allocated in board_f. The
gd->cur_serial_dev->driver->ops->putc points the the code region before
relocation.

Some serial drivers call WATCHDOG_RESET() in ops->putc. When DM is enabled
for watchdog, watchdog_reset() is called. watchdog_reset() calls get_timer
to get current timer.

On some platforms the timer driver is also a DM driver. initr_watchdog is
placed right after initr_dm, which means the timer driver hasn't been
initialized. So dm_timer_init() is called. To create a new udevice, calloc
is called.

However start from ops->putc, u-boot execution flow is redirected into the
memory region before relocation (board_f). In board_f, dlmalloc hasn't
been initialized. The call to calloc will fail, and this will cause DM to
print out an error message, and it will call printf again, causing
recursive error outputs.

This patch places initr_watchdog after initr_serial to solve this issue.

Cc: Stefan Roese <sr@denx.de>
Reviewed-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Tested-by: Suniel Mahesh <sunil.m@techveda.org>