memory: emif: Simplify code handling CONFIG_OF

memory: emif: Simplify code handling CONFIG_OF

The first thing that of_get_memory_device_details() does is calling
of_parse_phandle(). With CONFIG_OF=n this returns NULL in a static
inline function. So the compiler can determine that
of_get_memory_device_details() also returns NULL. bloat-o-meter confirms
that this patch has no effects on the size of the generated code for
CONFIG_OF=n builds.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/9d53683c34a730c8579a1468b643b11d1379106e.1702829744.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>