boot: fix false maybe-uninitialized warning

Fixes #25641.

src/boot/efi/boot.c

@@ -1550,7 +1550,7 @@ static EFI_STATUS efivar_get_timeout(const char16_t *var, uint32_t *ret_value) {
 
 static void config_load_defaults(Config *config, EFI_FILE *root_dir) {
         _cleanup_free_ char *content = NULL;
-        UINTN value;
+        UINTN value = 0;  /* avoid false maybe-uninitialized warning */
         EFI_STATUS err;
 
         assert(root_dir);
@@ -2233,7 +2233,7 @@ static void config_load_xbootldr(
                 EFI_HANDLE *device) {
 
         _cleanup_(file_closep) EFI_FILE *root_dir = NULL;
-        EFI_HANDLE new_device;
+        EFI_HANDLE new_device = NULL;  /* avoid false maybe-uninitialized warning */
         EFI_STATUS err;
 
         assert(config);

src/boot/efi/cpio.c

@@ -468,7 +468,7 @@ EFI_STATUS pack_cpio(
 
         for (UINTN i = 0; i < n_items; i++) {
                 _cleanup_free_ char *content = NULL;
-                UINTN contentsize;
+                UINTN contentsize = 0;  /* avoid false maybe-uninitialized warning */
 
                 err = file_read(extra_dir, items[i], 0, 0, &content, &contentsize);
                 if (err != EFI_SUCCESS) {

src/boot/efi/secure-boot.c

@@ -6,7 +6,7 @@
 #include "util.h"
 
 bool secure_boot_enabled(void) {
-        bool secure;
+        bool secure = false;  /* avoid false maybe-uninitialized warning */
         EFI_STATUS err;
 
         err = efivar_get_boolean_u8(EFI_GLOBAL_GUID, L"SecureBoot", &secure);