The imx-vpu library https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/imx-vpu-5.4.33.bin DOES support JPEG encode/decode on the i.MX6Q. I've been successfully using this library for over a year with a 3.14 kernel. There were gstreamer modules which also depended on this library, however they cannot work on later 4.x kernels.
Unfortunately, the /dev/mxc_vpu device is deprecated in 4.x kernels and replaced with the new coda V4L2 driver. Although the new coda driver supports H.264 encode/decode, it does not support JPEG on the i.MX6Q. Since the imx-vpu library contains source code to manage the Coda960 jpeg hardware, I wondered if anyone has looked into porting this support into the coda driver.