media: atomisp: Remove unnecessary NULL checks in ia_css_pipe_load_extension

Clang warns:

../drivers/staging/media/atomisp/pci/sh_css.c:8537:14: warning: address
of 'pipe->output_stage' will always evaluate to 'true'
[-Wpointer-bool-conversion]
                if (&pipe->output_stage)
                ~~   ~~~~~~^~~~~~~~~~~~
../drivers/staging/media/atomisp/pci/sh_css.c:8545:14: warning: address
of 'pipe->vf_stage' will always evaluate to 'true'
[-Wpointer-bool-conversion]
                if (&pipe->vf_stage)
                ~~   ~~~~~~^~~~~~~~

output_stage and vf_stage are pointers in the middle of a struct, their
addresses cannot be NULL if pipe is not NULL and pipe is already checked
for NULL in this function. Simplify this if block.

Link: https://github.com/ClangBuiltLinux/linux/issues/1036



Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>