MdeModulePkg/BMMUiLib: Replace same logic with API in UefiBootManagerLib
Use the API EfiBootManagerDeleteLoadOptionVariable in UefiBootManagerLib to
replace the same logic in function Var_DelBootOption/Var_DelDriverOption.
This can make code clean and prevent potential bugs.
Cc: Eric Dong <eric.dong@intel.com> Cc: Ruiyu Ni <ruiyu.ni@intel.com> Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Dandan Bi <dandan.bi@intel.com> Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com> Reviewed-by: Eric Dong <eric.dong@intel.com>