mmc: sdhci-bcm-kona: kill the "external_clk" member in driver private struct
mmc: sdhci-bcm-kona: kill the "external_clk" member in driver private struct

Actually we can use the "clk" in the struct sdhci_pltfm_host. Also
change the "external clock" to "core clock" and kill two redundant
private functions in this driver as suggested by Ray Jui.

Signed-off-by: Kevin Hao <7b5c7263b051e4f30fdb05a718aacc347c3275cd@gmail.com>
Reviewed-by: Ray Jui <16d3e9966b27c799b428e2cfa6c1218c3b78fa9c@broadcom.com>
Signed-off-by: Ulf Hansson <fe47b31f388f85ce6ddf64bf3a0cf6b46077d0e6@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs