drm/msm/dsi: Fix some reference counted resource leaks

drm/msm/dsi: Fix some reference counted resource leaks

'of_find_device_by_node()' takes a reference that must be released when
not needed anymore.
This is expected to be done in 'dsi_destroy()'.

However, there are 2 issues in 'dsi_get_phy()'.

First, if 'of_find_device_by_node()' succeeds but 'platform_get_drvdata()'
returns NULL, 'msm_dsi->phy_dev' will still be NULL, and the reference
won't be released in 'dsi_destroy()'.

Secondly, as 'of_find_device_by_node()' already takes a reference, there is
no need for an additional 'get_device()'.

Move the assignment to 'msm_dsi->phy_dev' a few lines above and remove the
unneeded 'get_device()' to solve both issues.

Fixes: ec31abf6684e ("drm/msm/dsi: Separate PHY to another platform device")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/f15bc57648a00e7c99f943903468a04639d50596.1628241097.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Rob Clark <robdclark@chromium.org>