efi_loader: add missing const qualifier

This commit fixes the following compilation warning
of boottime->install_configuration_table() function.

lib/efi_selftest/efi_selftest_tcg2.c:475:46:
warning: passing argument 1 of ‘boottime->install_configuration_table’
discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
  ret = boottime->install_configuration_table(&smbios_guid, dmi);

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index f0283b5..352c2db 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -1690,8 +1690,9 @@
  *
  * Return: status code
  */
-static efi_status_t EFIAPI efi_install_configuration_table_ext(efi_guid_t *guid,
-							       void *table)
+static efi_status_t
+EFIAPI efi_install_configuration_table_ext(const efi_guid_t *guid,
+					   void *table)
 {
 	EFI_ENTRY("%pUl, %p", guid, table);
 	return EFI_EXIT(efi_install_configuration_table(guid, table));