memory: omap-gpmc: deadcode a pair of functions

gpmc_get_client_irq() last use was removed by
commit ac28e47c ("ARM: OMAP2+: Remove legacy gpmc-nand.c")

gpmc_ticks_to_ns() last use was removed by
commit 2514830b ("ARM: OMAP2+: Remove gpmc-onenand")

Remove them.

gpmc_clk_ticks_to_ns() is now only used in some DEBUG
code; move inside the ifdef to avoid unused warnings.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20241211214227.107980-1-linux@treblig.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>