efi_loader: Fix capsule_esl.dtsi.in comment style

Comment is not kernel-doc format that's why don't label it like that and
also fix indentation to have proper multiline comment.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/lib/efi_loader/capsule_esl.dtsi.in b/lib/efi_loader/capsule_esl.dtsi.in
index 61a9f2b..bc7db83 100644
--- a/lib/efi_loader/capsule_esl.dtsi.in
+++ b/lib/efi_loader/capsule_esl.dtsi.in
@@ -1,9 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0+
-/**
+/*
  * Devicetree file with the public key EFI Signature List(ESL)
  * node. This file is used to generate the dtsi file to be
  * included into the DTB.
-*/
+ */
 / {
 	signature {
 		capsule-key = /incbin/("ESL_BIN_FILE");