mmc: spear: remove the entire spear_sdhci.c file

Remove the entire spear_sdhci.c file.
There is no use case. This is dead codes.
Also there is no place to call "spear_sdhci_init()" anywhere.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Tom Rini <trini@konsulko.com>