powerpc: wii.dts: Reduce the size of the control area

This is wrong, but needed in order to avoid overlapping ranges with the
OTP area added in the next commit.  A refactor of this part of the
device tree is needed: according to Wiibrew[1], this area starts at
0x0d800000 and spans 0x400 bytes (that is, 0x100 32-bit registers),
encompassing PIC and GPIO registers, amongst the ones already exposed in
this device tree, which should become children of the control@d800000
node.

[1] https://wiibrew.org/wiki/Hardware/Hollywood_Registers



Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210801073822.12452-4-linkmauve@linkmauve.fr