mips: sgi-ip27: switch from DISCONTIGMEM to SPARSEMEM

The memory initialization of SGI-IP27 is already half-way to support
SPARSEMEM. It only had free_bootmem_with_active_regions() left-overs
interfering with sparse_memory_present_with_active_regions().

Replace these calls with simpler memblocks_present() call in prom_meminit()
and adjust arch/mips/Kconfig to enable SPARSEMEM and SPARSEMEM_EXTREME for
SGI-IP27.

Co-developed-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 8736bf4..a4ce359 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -674,6 +674,7 @@
 config SGI_IP27
 	bool "SGI IP27 (Origin200/2000)"
 	select ARCH_HAS_PHYS_TO_DMA
+	select ARCH_SPARSEMEM_ENABLE
 	select FW_ARC
 	select FW_ARC64
 	select BOOT_ELF64
@@ -2618,18 +2619,9 @@
 	def_bool y
 	depends on !NUMA && !CPU_LOONGSON2
 
-config ARCH_DISCONTIGMEM_ENABLE
-	bool
-	default y if SGI_IP27
-	help
-	  Say Y to support efficient handling of discontiguous physical memory,
-	  for architectures which are either NUMA (Non-Uniform Memory Access)
-	  or have huge holes in the physical address space for other reasons.
-	  See <file:Documentation/vm/numa.rst> for more.
-
 config ARCH_SPARSEMEM_ENABLE
 	bool
-	select SPARSEMEM_STATIC
+	select SPARSEMEM_STATIC if !SGI_IP27
 
 config NUMA
 	bool "NUMA Support"