watchdog: iTCO: fix link error

When the MFD driver is a loadable module, the watchdog driver fails
to get linked into the kernel:

drivers/watchdog/iTCO_wdt.o: In function `update_no_reboot_bit_pmc':
iTCO_wdt.c:(.text+0x54f): undefined reference to `intel_pmc_gcr_update'

The code is written to support operation without the MFD driver, so
add a Kconfig dependency that allows this, while disallowing the watchdog
to be built-in when the MFD driver is a module.

Fixes: 25f1ca3 ("platform/x86: intel_pmc_ipc: Convert to MFD")
Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Guenter Roeck <[email protected]>
Reviewed-by: Mika Westerberg <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>

Author: arndb

drivers/watchdog/Kconfig

@@ -1218,6 +1218,7 @@ config ITCO_WDT
 	depends on (X86 || IA64) && PCI
 	select WATCHDOG_CORE
 	depends on I2C || I2C=n
+	depends on MFD_INTEL_PMC_BXT || !MFD_INTEL_PMC_BXT
 	select LPC_ICH if !EXPERT
 	select I2C_I801 if !EXPERT && I2C
 	---help---