mmc: sdhci-omap: Remove forward declaration of sdhci_omap_context_save()

If CONFIG_PM_SLEEP=n:

    drivers/mmc/host/sdhci-omap.c:1213:13: error: ‘sdhci_omap_context_save’ declared ‘static’ but never defined [-Werror=unused-function]
     1213 | static void sdhci_omap_context_save(struct sdhci_omap_host *omap_host);
	  |             ^~~~~~~~~~~~~~~~~~~~~~~

The referenced commit added an unrelated forward declaration of
sdhci_omap_context_save(), which is unneeded in general, and unused when
CONFIG_PM_SLEEP=n.

Fixes: f433e8aa ("mmc: sdhci-omap: Implement PM runtime functions")
Reported-by:  <noreply@ellerman.id.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20211020083902.3669769-1-geert@linux-m68k.org


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>