memory: omap-gpmc: fix wait pin validation

memory: omap-gpmc: fix wait pin validation

This bug has been introduced after switching from -1 to UINT_MAX
for GPMC_WAITPIN_INVALID.

The bug leads to an error when the optional gpmc,wait-pin
dt-property is not used:

...
gpmc_cs_program_settings: invalid wait-pin (-1)
...

Signed-off-by: Benedikt Niedermayr <benedikt.niedermayr@siemens.com>
Fixes: 8dd7e4af5853 ("memory: omap-gpmc: fix coverity issue "Control flow issues"")
Acked-by: Roger Quadros <rogerq@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20221209112828.581491-1-benedikt.niedermayr@siemens.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>