opp: Fix error check in dev_pm_opp_attach_genpd()

opp: Fix error check in dev_pm_opp_attach_genpd()

[ Upstream commit 6d935a10e2f19d8102ebc56c731a5bf07c373815 ]

dev_pm_domain_attach_by_name() may return NULL in some cases,
so IS_ERR() doesn't meet the requirements. Thus fix it.

Fixes: 2d395697182c ("opp: Attach genpds to devices from within OPP core")
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
[ Viresh: Replace ENODATA with ENODEV ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>