ARM: ep93xx: switch to SPARSEMEM

The EP93xx has four chip selects that can be used for the SDRAM memory.
These chip selects are decoded to specify an address domain:

  SDCS3  0x00000000-0x0fffffff with Boot Option ASDO=1
  SDCS0  0xc0000000-0xcfffffff
  SDCS1  0xd0000000-0xdfffffff
  SDCS2  0xe0000000-x0efffffff
  SDCS3  0xf0000000-0xffffffff with Boot Option ASDO=0

Because of the row/column/bank architecture of SDRAM, the mapping of
these memories into the processor's memory space is discontiguous.

Most ep93xx systems only use one of the chip selects. For these systems,
ARCH_HAS_HOLES_MEMORYMODEL has worked fine to handle the discontiguous
memory.

But, some of the TS-72xx boards use multiple chip selects. The TS-7300 in
particular uses SDCS3 (with ASDO=1) and SDCS2. On that system with
ARCH_HAS_HOLES_MEMORYMODEL the SDCS2 memory does not get handled correctly
and results in the system not booting.

Change the EP93xx to ARCH_SPARSEMEM_ENABLE. This handles the discontiguous
memory for all configurations.

This has been tested on the following ep93xx platforms:

EDB9307A with 64 MiB on SDCS0
Vision EP9307 with 64 MiB on SDCS0
TS-7300 with 64 MiB on SDCS3 (with ASDO=1) and 64 MiB on SDCS2
sim.one with 64 MiB on SDCS0

Signed-off-by: H Hartley Sweeten <[email protected]>
Tested-by: Linus Walleij <[email protected]>
Cc: Russell King <[email protected]>
Tested-by: Florian Fainelli <[email protected]>
Tested-by: Alexander Sverdlin <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>

arch/arm/Kconfig

@@ -378,7 +378,7 @@ config ARCH_EBSA110
 
 config ARCH_EP93XX
 	bool "EP93xx-based"
-	select ARCH_HAS_HOLES_MEMORYMODEL
+	select ARCH_SPARSEMEM_ENABLE
 	select ARM_AMBA
 	imply ARM_PATCH_PHYS_VIRT
 	select ARM_VIC