[nrf fromlist] mgmt: mcumgr: grp: os_mgmt: Fix compilation warning

This is a follow up to commit 770482a.

Add initialization of the `ok` variable to prevent the "may be
uninitialized" warning when `CONFIG_BOOTLOADER_MCUBOOT` is not
defined.

Upstream PR #: 84101

Signed-off-by: Andrzej Głąbek <[email protected]>

Author: anangl

subsys/mgmt/mcumgr/grp/os_mgmt/src/os_mgmt.c

@@ -450,7 +450,7 @@ os_mgmt_bootloader_info(struct smp_streamer *ctxt)
 	zcbor_state_t *zsd = ctxt->reader->zs;
 	struct zcbor_string query = { 0 };
 	size_t decoded;
-	bool ok;
+	bool ok = true;
 	bool has_output = false;
 
 #if defined(CONFIG_MCUMGR_GRP_OS_BOOTLOADER_INFO_HOOK)