media: hantro: Check whether reset op is defined before use

In the Linux kernel, the following vulnerability has been resolved:

media: hantro: Check whether reset op is defined before use

The i.MX8MM/N/P does not define the .reset op since reset of the VPU is

done by genpd. Check whether the .reset op is defined before calling it

to avoid NULL pointer dereference.

Note that the Fixes tag is set to the commit which removed the reset op

from i.MX8M Hantro G2 implementation, this is because before this commit

all the implementations did define the .reset op.