ARM: pxa: trizeps4 and trizeps4wl use the same file

The trizeps4 and trizeps4wl platforms are both implemented
using the same board file. Since the trizeps4wl code is a
superset of trizeps4, it makes no sense to enable just the
latter, but with the current Kconfig logic, it causes the
board file not to be built at all.

Selecting MACH_TRIZEPS4 from MACH_TRIZEPS4WL ensures that
we are actually building the board file.

Found during randconfig testing.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Daniel Mack <zonque@gmail.com>