MdeModulePkg: Use BmCharToUint in BmIsKeyOptionVariable

The patch also moves the BmCharToUint to BmMisc.c because it
belongs to misc functions.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Sunny Wang <sunnywang@hpe.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18855 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c

@@ -586,29 +586,6 @@ EfiBootManagerDeleteLoadOptionVariable (
   return Status;
 }
 
-/**
-  Convert a single character to number.
-  It assumes the input Char is in the scope of L'0' ~ L'9' and L'A' ~ L'F'
-
-  @param    Char   The input char which need to convert to int.
-**/
-UINTN
-BmCharToUint (
-  IN CHAR16                           Char
-  )
-{
-  if ((Char >= L'0') && (Char <= L'9')) {
-    return (UINTN) (Char - L'0');
-  }
-
-  if ((Char >= L'A') && (Char <= L'F')) {
-    return (UINTN) (Char - L'A' + 0xA);
-  }
-
-  ASSERT (FALSE);
-  return (UINTN) -1;
-}
-
 /**
   Returns the size of a device path in bytes.