arm: remove zte zx platform left-over

arm: remove zte zx platform left-over

Commit 89d4f98ae90d ("ARM: remove zte zx platform") missed to remove some
definitions for this platform's debug and serial, e.g., code dependent on
the config DEBUG_ZTE_ZX.

Fortunately, ./scripts/checkkconfigsymbols.py detects this and warns:

DEBUG_ZTE_ZX
Referencing files: arch/arm/include/debug/pl01x.S

Further review by Arnd Bergmann identified even more dead code in the
amba serial driver.

Remove all this left-over from the zte zx platform.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20211102063810.932-1-lukas.bulwahn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>