efi_loader: use LOGC_EFI consistently

The log category should be LOGC_EFI all over the EFI sub-system.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

lib/efi_loader/efi_root_node.c

@@ -5,6 +5,8 @@
  *  Copyright (c) 2018 Heinrich Schuchardt
  */
 
+#define LOG_CATEGORY LOGC_EFI
+
 #include <malloc.h>
 #include <efi_dt_fixup.h>
 #include <efi_loader.h>