scsi: pmcraid: use __iomem pointers for ioctl argument

kernelci.org reports a new compile warning for old code in the pmcraid
driver:

arch/mips/include/asm/uaccess.h:138:21: warning: passing argument 1 of '__access_ok' makes pointer from integer without a cast [-Wint-conversion]

The warning got introduced by a cleanup to the access_ok() helper that
requires the argument to be a pointer, where the old version silently
accepts 'unsigned long' arguments as it still does on most other
architectures.

The new behavior in MIPS however seems absolutely sensible, and so far I
could only find one other file with the same issue, so the best solution
seems to be to clean up the pmcraid driver.

This makes the driver consistently use 'void __iomem *' pointers for
passing around the address of the user space ioctl arguments, which gets
rid of the kernelci warning as well as several sparse warnings.

Fixes: f0a955f4 ("mips: sanitize __access_ok()")
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>