MIPS: Routerboard 532: Fix vendor retry check code

MIPS: Routerboard 532: Fix vendor retry check code

read_config_dword() contains strange condition checking ret for a
number of values. The ret variable, however, is always zero because
config_access() never returns anything else. Thus, the retry is always
taken until number of tries is exceeded.

The code looks like it wants to check *val instead of ret to see if the
read gave an error response.

Fixes: 73b4390fb234 ("[MIPS] Routerboard 532: Support for base system")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>