gpu: host1x: Fix error handling

If 'devm_reset_control_get' returns an error, then we erroneously return
success because error code is taken from 'host->clk' instead of
'host->rst'.

Fixes: b386c6b7

 ("gpu: host1x: Support module reset")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170410202922.17665-1-christophe.jaillet@wanadoo.fr