uacce: remove uacce_vma_fault

Fix NULL pointer error if removing uacce's parent module during app's
running. SIGBUS is already reported by do_page_fault, so uacce_vma_fault
is not needed. If providing vma_fault, vmf->page has to be filled as well,
required by __do_fault.

Reported-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/1592229357-1904-1-git-send-email-zhangfei.gao@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>