drivers/mmc/dw_mmc - remove extra arch specific "asm/arch/clk.h" inclusion

drivers/mmc/dw_mmc - remove extra arch specific "asm/arch/clk.h" inclusion

1. No contents of "asm/arch/clk.h" is used within "dw_mmc.c".
2. If arch doesn't have "asm/arch/clk.h" driver won't build.

Without mentioned inclusion dw_mmc driver could be built for arches
other than ARM. For ARM driver still builds without it.

Signed-off-by: Alexey Brodkin <[email protected]>
Cc: Mischa Jonker <[email protected]>
Cc: Andy Fleming <[email protected]>
Cc: Rajeshwari Shinde <[email protected]>
Cc: Amar <[email protected]>
Cc: Minkyu Kang <[email protected]>
Cc: Jaehoon Chung <[email protected]>
Signed-off-by: Andy Fleming <[email protected]>