[PATCH] mmc: cv1800b: Fix build without MMC_SUPPORTS_TUNING

[Peng Fan]

> Subject: [PATCH] mmc: cv1800b: Fix build without
> MMC_SUPPORTS_TUNING
> 
> That's how it looks like without CONFIG_MMC_SUPPORTS_TUNING
> before the
> patch:
> 
> aarch64-buildroot-linux-gnu-ld.bfd: drivers/mmc/cv1800b_sdhci.o: in
> function `cv1800b_execute_tuning':
> drivers/mmc/cv1800b_sdhci.c:47:(.text.cv1800b_execute_tuning+0x50
> ): undefined reference to `mmc_send_tuning'
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin at gmail.com>

Reviewed-by: Peng Fan <peng.fan at nxp.com>