GPIO: gpio-pxa: fix building without CONFIG_OF

Commit 72121572 ("GPIO: gpio-pxa: fix devicetree functions") added an
"xlate" function pointer to the irq_domain_ops, but this function is nor
declared or defined anywhere when CONFIG_OF is disabled, causing the
build error:

  drivers/gpio/gpio-pxa.c:532:11: error: 'irq_domain_xlate_twocell' undeclared here (not in a function)

Extending the DT-only code section to cover the irq_domain_ops and the
pxa_gpio_dt_ids solves this problem and makes it clearer which code is
actually used without DT.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>