ia64: make SPARSEMEM default and disable DISCONTIGMEM

SPARSEMEM memory model suitable for systems with large holes in their
phyiscal memory layout. With SPARSEMEM_VMEMMAP enabled it provides
pfn_to_page() and page_to_pfn() as fast as FLATMEM.

Make it the default memory model for IA-64 and disable DISCONTIGMEM which
is considered obsolete for quite some time.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: John Paul Adrian Glaubitz <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Meelis Roos <[email protected]>
Cc: Michael Schmitz <[email protected]>
Cc: Russell King <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/ia64/Kconfig

@@ -288,6 +288,7 @@ config ARCH_SELECT_MEMORY_MODEL
 
 config ARCH_DISCONTIGMEM_ENABLE
 	def_bool y
+	depends on BROKEN
 	help
 	  Say Y to support efficient handling of discontiguous physical memory,
 	  for architectures which are either NUMA (Non-Uniform Memory Access)
@@ -299,12 +300,11 @@ config ARCH_FLATMEM_ENABLE
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on ARCH_DISCONTIGMEM_ENABLE
 	select SPARSEMEM_VMEMMAP_ENABLE
 
-config ARCH_DISCONTIGMEM_DEFAULT
+config ARCH_SPARSEMEM_DEFAULT
 	def_bool y
-	depends on ARCH_DISCONTIGMEM_ENABLE
+	depends on ARCH_SPARSEMEM_ENABLE
 
 config NUMA
 	bool "NUMA support"