switch from "rmmod" to "modprobe -r"

switch from "rmmod" to "modprobe -r"

Origin: upstream, https://github.com/Bumblebee-Project/Bumblebee/commit/1ada79fe5916961fc4e4917f8c63bb184908d986
Bug: https://github.com/Bumblebee-Project/Bumblebee/issues/565
Bug-Debian: https://bugs.debian.org/793389

With the introduction of nvidia-uvm module, unloading nvidia module will fail
unless nvidia-uvm is unloaded.  GH-565 suggests using "remove" or "softdep"
modprobe.d clauses to teach modprobe to handle that for us; "rmmod" does not
have that functionality, so switch to "modprobe -r".

Gbp-Pq: Name modprobe-r-instead-of-rmmod.patch