The USB host drivers need platform data to be defined on
pxa168 and pxa910, but the conditionals used in the devices.c
file only work if the drivers are built-in. This patch
fixes the definition by changing the #ifdef to #if IS_ENABLED(),
which works both for built-in and modular Kconfig symbols.

I found one specific problem using 'randconfig' builds, but
for consistency, this patch uses IS_ENABLED() for all Kconfig
symbols in these three files.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>