Use a compare operator for Non-Boolean comparison in 'map.c'.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Jaben carsey <Jaben.carsey@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15559 6f19259b-4bc3-4df7-8a09-765794883524