MdeModulePkg/XhciDxe: Dynamically calculate the interval value of interrupt endpoint context of low/full speed device behind low/full speed hub.

Signed-off-by: Tian, Feng <feng.tian@intel.com>
reviewed-by: Li, Elvin <elvin.li@intel.com>


git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@14797 6f19259b-4bc3-4df7-8a09-765794883524