eeprom: at25: Add DT support for EEPROMs with odd address bits

Certain EEPROMS have a size that is larger than the number of address
bytes would allow, and store the MSB of the address in bit 3 of the
instruction byte.

This can be described in platform data using EE_INSTR_BIT3_IS_ADDR, or
in DT using the obsolete legacy "at25,addr-mode" property.
But currently there exists no non-deprecated way to describe this in DT.

Hence extend the existing "address-width" DT property to allow
specifying 9 address bits, and enable support for that in the driver.

This has been tested with a Microchip 25LC040A.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>