x86: make sparsemem more available

With CONFIG_X86_PC, I can set CONFIG_SPARSEMEM=y.

With CONFIG_X86_GENERICARCH, CONFIG_SPARSEMEM depends on CONFIG_NUMA.

I'm using the patch below to enable sparsemem instead of flatmem.
System booted and is running.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -1035,7 +1035,7 @@ config HAVE_ARCH_ALLOC_REMAP
 
 config ARCH_FLATMEM_ENABLE
 	def_bool y
-	depends on X86_32 && ARCH_SELECT_MEMORY_MODEL && X86_PC && !NUMA
+	depends on X86_32 && ARCH_SELECT_MEMORY_MODEL && !NUMA
 
 config ARCH_DISCONTIGMEM_ENABLE
 	def_bool y
@@ -1051,7 +1051,7 @@ config ARCH_SPARSEMEM_DEFAULT
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on X86_64 || NUMA || (EXPERIMENTAL && X86_PC)
+	depends on X86_64 || NUMA || (EXPERIMENTAL && X86_PC) || X86_GENERICARCH
 	select SPARSEMEM_STATIC if X86_32
 	select SPARSEMEM_VMEMMAP_ENABLE if X86_64