ARM: dts: Fix wrong GPMC size mappings for omaps

The GPMC binding is obviously very confusing as the values
are all over the place. People seem to confuse the GPMC partition
size for the chip select, and the device IO size within the GPMC
partition easily.

The ranges entry contains the GPMC partition size. And the
reg entry contains the size of the IO registers of the
device connected to the GPMC.

Let's fix the issue according to the following table:

Device          GPMC partition size     Device IO size
connected       in the ranges entry     in the reg entry

NAND            0x01000000 (16MB)       4
16550           0x01000000 (16MB)       8
smc91x          0x01000000 (16MB)       0xf
smc911x         0x01000000 (16MB)       0xff
OneNAND         0x01000000 (16MB)       0x20000 (128KB)
16MB NOR        0x01000000 (16MB)       0x01000000 (16MB)
32MB NOR        0x02000000 (32MB)       0x02000000 (32MB)
64MB NOR        0x04000000 (64MB)       0x04000000 (64MB)
128MB NOR       0x08000000 (128MB)      0x08000000 (128MB)
256MB NOR       0x10000000 (256MB)      0x10000000 (256MB)

Let's also add comments to the fixed entries while at it.

Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>