x86/platform: Add PCI dependency for PUNIT_ATOM_DEBUG

The IOSF_MBI option requires PCI support, without it we get a harmless
Kconfig warning when it gets selected by PUNIT_ATOM_DEBUG:

  warning: (X86_INTEL_LPSS && SND_SST_IPC_ACPI && MMC_SDHCI_ACPI && PUNIT_ATOM_DEBUG) selects IOSF_MBI which has unmet direct dependencies (PCI)

This adds another dependency to avoid the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170719125310.2487451-8-arnd@arndb.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/Kconfig.debug

@@ -348,6 +348,7 @@ config X86_DEBUG_FPU
 
 config PUNIT_ATOM_DEBUG
 	tristate "ATOM Punit debug driver"
+	depends on PCI
 	select DEBUG_FS
 	select IOSF_MBI
 	---help---