Fix the __iomem annotation of the iomem_base pointers in the apple-gmux
code. The __iomem should go before the *.

This fixes a bunch of sparse warnings like this one:

drivers/platform/x86/apple-gmux.c:224:48: sparse:
 expected void const [noderef] __iomem *
 got unsigned char [usertype] *

Fixes: 0c18184d ("platform/x86: apple-gmux: support MMIO gmux on T2 Macs")
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202304040401.IMxt7Ubi-lkp@intel.com/Suggested-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Orlando Chamberlain <orlandoch.dev@gmail.com>
Link: https://lore.kernel.org/r/20230404111955.43266-1-hdegoede@redhat.com