Add patch to enable successful builds for Leap 15.5.

The dma-buf symbols used by this driver were moved into their own `DMA_BUF`
module namespace in kernel 5.16. Consequently, the upstream source conditionally
imports the `DMA_BUF` module namespace if the kernel version is >= 5.16.

However, the `DMA_BUF` module namespace changes have been backported to the
5.14 kernel used in Leap 15.5, causing unpatched source builds to fail.

This change incorporates a patch that removes the conditional check in the
upstream source, importing the `DMA_BUF` module namespace regardless of kernel
version, and applies that patch when `sle_version` is equal to "150500"
(ie. is Leap 15.5 or greater).

The patch is taken from the PR at:
https://github.com/google/gasket-driver/pull/10