ARM: LPC32xx: Fix reset function

In the recent change to the reset function API (commit
7b6d864b48d95e6ea1df7df64475b9cb9616dcf9), the mode argument changed from a
char to an enum. lpc23xx_restart() only handles REBOOT_SOFT and REBOOT_HARD,
but the new kernel code emits REBOOT_COLD (0) on reboots now which leads to
lpc32xx simply not rebooting (but halting).

This patch fixes this by just resetting unconditionally as on other platforms
(e.g. mach-bcm2835).

Pulling lpc32xx_watchdog_reset() into lpc23xx_restart() since the while() in
lpc23xx_restart() is part of the procedure anyway and lpc32xx_watchdog_reset()
isn't used anywhere else anymore.

Signed-off-by: Roland Stigge <stigge@antcom.de>