platform/x86: p2sb: Make the Kconfig symbol hidden

The P2SB is used purely as a library and all users must select it with

	depends on PCI
	select P2SB if X86

statement. Without this the combination of different configuration
options may lead to build failures.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230822142514.2140897-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/Kconfig

@@ -1103,7 +1103,7 @@ config SEL3350_PLATFORM
 endif # X86_PLATFORM_DEVICES
 
 config P2SB
-	bool "Primary to Sideband (P2SB) bridge access support"
+	bool
 	depends on PCI && X86
 	help
 	  The Primary to Sideband (P2SB) bridge is an interface to some