package/paho-mqtt-c: bump version to 1.3.15

Release notes:
https://github.com/eclipse-paho/paho.mqtt.c/releases/tag/v1.3.15

Signed-off-by: Scott Fan <fancp2007@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/paho-mqtt-c/paho-mqtt-c.hash

@@ -1,5 +1,5 @@
 # Locally computed:
-sha256  7af7d906e60a696a80f1b7c2bd7d6eb164aaad908ff4c40c3332ac2006d07346  paho-mqtt-c-1.3.14.tar.gz
+sha256  60ce2cfdc146fcb81c621cb8b45874d2eb1d4693105d048f60e31b8f3468be90  paho-mqtt-c-1.3.15.tar.gz
 sha256  83bbba033dc985487e321b6dfde111772affb73460be48726299fed3da684b1c  edl-v10
 sha256  0becf16567beb77fa252b7664631dd177c8f9a1889e48995b45379c7130e5303  epl-v20
 sha256  bc0f3f447097eb82a29ad6c2f4929572bb548b6bd4c9e38fde1bf131a771b7a0  LICENSE

package/paho-mqtt-c/paho-mqtt-c.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-PAHO_MQTT_C_VERSION = 1.3.14
+PAHO_MQTT_C_VERSION = 1.3.15
 PAHO_MQTT_C_SITE = $(call github,eclipse,paho.mqtt.c,v$(PAHO_MQTT_C_VERSION))
 PAHO_MQTT_C_LICENSE = EPL-2.0 or BSD-3-Clause
 PAHO_MQTT_C_LICENSE_FILES = epl-v20 edl-v10 LICENSE