staging: rts5208: fix missing error check on call to rtsx_write_register

staging: rts5208: fix missing error check on call to rtsx_write_register

[ Upstream commit c5fae4f4fd28189b1062fb8ef7b21fec37cb8b17 ]

Currently the check on error return from the call to rtsx_write_register
is checking the error status from the previous call. Fix this by adding
in the missing assignment of retval.

Detected by CoverityScan, CID#709877

Fixes: fa590c222fba ("staging: rts5208: add support for rts5208 and rts5288")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>