efi_loader: use u16_strlen() in efi_var_mem_ins()

Don't duplicate library functionality.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_var_mem.c b/lib/efi_loader/efi_var_mem.c
index 0bac594..e1058e3 100644
--- a/lib/efi_loader/efi_var_mem.c
+++ b/lib/efi_loader/efi_var_mem.c
@@ -146,9 +146,7 @@
 
 	var = (struct efi_var_entry *)
 	      ((uintptr_t)efi_var_buf + efi_var_buf->length);
-	for (var_name_len = 0; variable_name[var_name_len]; ++var_name_len)
-		;
-	++var_name_len;
+	var_name_len = u16_strlen(variable_name) + 1;
 	data = var->name + var_name_len;
 
 	if ((uintptr_t)data - (uintptr_t)efi_var_buf + size1 + size2 >