cmd: Remove mmc_spi command

The mmc_spi command was added to manually setup MMC over SPI bus
using command. This was required by the legacy non-DM MMC_SPI driver.

With DM based MMC_SPI driver in-place, we can now use all general
storge commands and mmc command for MMC over SPI bus hence we remove
the mmc_spi command all it's references.

Suggested-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/configs/UCP1020.h

@@ -438,7 +438,6 @@
 
 #ifdef CONFIG_MMC
 #define CONFIG_SYS_FSL_ESDHC_ADDR	CONFIG_SYS_MPC85xx_ESDHC_ADDR
-#define CONFIG_MMC_SPI
 #endif
 
 /* Misc Extra Settings */

include/mmc.h

@@ -824,7 +824,6 @@ void mmc_set_preinit(struct mmc *mmc, int preinit);
 #else
 #define mmc_host_is_spi(mmc)	0
 #endif
-struct mmc *mmc_spi_init(uint bus, uint cs, uint speed, uint mode);
 
 void board_mmc_power_init(void);
 int board_mmc_init(bd_t *bis);