Add 'volatile' to iounmap()'s argument to prevent build warnings.
This make it the same as other major architectures.
Placates these warnings: (12 such warnings)
../drivers/video/fbdev/riva/fbdev.c: In function 'rivafb_probe':
../drivers/video/fbdev/riva/fbdev.c:2067:42: error: passing argument 1 of 'iounmap' discards 'volatile' qualifier from pointer target type [-Werror=discarded-qualifiers]
2067 | iounmap(default_par->riva.PRAMIN);
Fixes: 1162b0701b14b ("ARC: I/O and DMA Mappings")
Signed-off-by: Randy Dunlap<rdunlap@xxxxxxxxxxxxx>
Cc: Vineet Gupta<vgupta@xxxxxxxxxx>
Cc:linux-snps-arc@xxxxxxxxxxxxxxxxxxx
Cc: Arnd Bergmann<arnd@xxxxxxxx>