drm/nouveau/fb: restore init() for ramgp102

init() was removed from ramgp102 when reworking the memory detection, as
it was thought that the code was only necessary when the driver performs
mclk changes, which nouveau doesn't support on pascal.

However, it turns out that we still need to execute this on some GPUs to
restore settings after DEVINIT, so revert to the original behaviour.

v2: fix tags in commit message, cc stable

Closes: https://gitlab.freedesktop.org/drm/nouveau/-/issues/319


Fixes: 2c0c15a2 ("drm/nouveau/fb/gp102-ga100: switch to simpler vram size detection method")
Cc: stable@vger.kernel.org # 6.6+
Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240904232418.8590-1-bskeggs@nvidia.com