x86/Kconfig: Merge the two CONFIG_X86_EXTENDED_PLATFORM entries

There are two menu entries for X86_EXTENDED_PLATFORM, one for X86_32 and
the other for X86_64.

These entries are nearly identical, with the only difference being the
platform list in the help message.

While this structure was intended by commit

  8425091f ("x86: improve the help text of X86_EXTENDED_PLATFORM"),

there is no need to duplicate the entire config entry. Instead, provide
a little more clarification in the help message.

  [ bp: Massage. ]
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240204100719.42574-1-masahiroy@kernel.org

arch/x86/Kconfig

@@ -506,10 +506,9 @@ config X86_FRED
 	  ring transitions and exception/interrupt handling if the
 	  system supports.
 
-if X86_32
 config X86_BIGSMP
 	bool "Support for big SMP systems with more than 8 CPUs"
-	depends on SMP
+	depends on SMP && X86_32
 	help
 	  This option is needed for the systems that have more than 8 CPUs.
 
@@ -522,7 +521,10 @@ config X86_EXTENDED_PLATFORM
 	  systems out there.)
 
 	  If you enable this option then you'll be able to select support
-	  for the following (non-PC) 32 bit x86 platforms:
+	  for the following non-PC x86 platforms, depending on the value of
+	  CONFIG_64BIT.
+
+	  32-bit platforms (CONFIG_64BIT=n):
 		Goldfish (Android emulator)
 		AMD Elan
 		RDC R-321x SoC
@@ -530,28 +532,14 @@ config X86_EXTENDED_PLATFORM
 		STA2X11-based (e.g. Northville)
 		Moorestown MID devices
 
-	  If you have one of these systems, or if you want to build a
-	  generic distribution kernel, say Y here - otherwise say N.
-endif # X86_32
-
-if X86_64
-config X86_EXTENDED_PLATFORM
-	bool "Support for extended (non-PC) x86 platforms"
-	default y
-	help
-	  If you disable this option then the kernel will only support
-	  standard PC platforms. (which covers the vast majority of
-	  systems out there.)
-
-	  If you enable this option then you'll be able to select support
-	  for the following (non-PC) 64 bit x86 platforms:
+	  64-bit platforms (CONFIG_64BIT=y):
 		Numascale NumaChip
 		ScaleMP vSMP
 		SGI Ultraviolet
 
 	  If you have one of these systems, or if you want to build a
 	  generic distribution kernel, say Y here - otherwise say N.
-endif # X86_64
+
 # This is an alphabetically sorted list of 64 bit extended platforms
 # Please maintain the alphabetic order if and when there are additions
 config X86_NUMACHIP