MdeModulePkg/SdMmcPciHcDxe: Remove clock stop from HS200 switch

MdeModulePkg/SdMmcPciHcDxe: Remove clock stop from HS200 switch

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2218

Stopping the SD clock before switching host controller
bus timing is only necessary if preset value enable is
set in host controller. Code that performs switch to
HS200 doesn't check this condition right now and we also
don't do the SD clock stop before any other bus timing switch
in host controller. Since the driver is generally not ready to support
host controller with preset value enable set we removed this
code.

Signed-off-by: Mateusz Albecki <mateusz.albecki@intel.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>
Tested-by: Hao A Wu <hao.a.wu@intel.com>
Tested-by: Marcin Wojtas <mw@semihalf.com>