Input: gscps2 - check return value of ioremap() in gscps2_probe()

The function ioremap() in gscps2_probe() can fail, so
its return value should be checked.

Fixes: 4bdc0d67

 ("remove ioremap_nocache and devm_ioremap_nocache")
Cc: <stable@vger.kernel.org> # v5.6+
Reported-by: Hacash Robot <hacashRobot@santino.com>
Signed-off-by: Xie Shaowen <studentxswpy@163.com>
Signed-off-by: Helge Deller <deller@gmx.de>