kernel/x86: move x86' specific watchdogs to the x86 target

kernel/x86: move x86' specific watchdogs to the x86 target

upstream linux have these watchdogs locked behind X86.
These will not build on other architectures. So move them
to target/linux/x86/modules.mk

drivers/watchdog/Kconfig:

|config F71808E_WDT
|	tristate "Fintek F718xx, F818xx Super I/O Watchdog"
|	depends on X86
|[...]
|config IT87_WDT
|	tristate "IT87 Watchdog Timer"
|	depends on X86
|[...]
|config ITCO_WDT
|	tristate "Intel TCO Timer/Watchdog"
|	depends on (X86 || IA64) && PCI
|[...]
|config W83627HF_WDT
|	tristate "Watchdog timer for W83627HF/W83627DHG and compatibles"
|	depends on X86
|[...]

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>