ARM: dts: dra7x-evm: Drop "ti,pcf8575"

The TI part is equivalent to the NXP part and its compatible value is
not documented in the DT bindings.  All other users of similar I2C GPIO
expanders just use the compatible values of the original NXP parts.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Tony Lindgren <tony@atomide.com>