arm_mpam: Force __iomem casts

Code allocates standard kernel memory to pass to the MPAM, which expects
__iomem.  The code is safe, because __iomem accessors should work fine
on kernel mapped memory, however leads to sparse warnings:

  test_mpam_devices.c:327:42: warning: incorrect type in initializer (different address spaces)
  test_mpam_devices.c:327:42:    expected char [noderef] __iomem *buf
  test_mpam_devices.c:327:42:    got void *
  test_mpam_devices.c:342:24: warning: cast removes address space '__iomem' of expression

Cast the pointer to memory via __force to silence them.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512160133.eAzPdJv2-lkp@intel.com/
Acked-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Author: krzk

drivers/resctrl/test_mpam_devices.c

@@ -332,7 +332,7 @@ static void __test_mpam_reset_msc_bitmap(struct mpam_msc *msc, u16 reg, u16 wd)
 
 static void test_mpam_reset_msc_bitmap(struct kunit *test)
 {
-	char __iomem *buf = kunit_kzalloc(test, SZ_16K, GFP_KERNEL);
+	char __iomem *buf = (__force char __iomem *)kunit_kzalloc(test, SZ_16K, GFP_KERNEL);
 	struct mpam_msc fake_msc = {};
 	u32 *test_result;
 
@@ -347,7 +347,7 @@ static void test_mpam_reset_msc_bitmap(struct kunit *test)
 	mutex_init(&fake_msc.part_sel_lock);
 	mutex_lock(&fake_msc.part_sel_lock);
 
-	test_result = (u32 *)(buf + MPAMCFG_CPBM);
+	test_result = (__force u32 *)(buf + MPAMCFG_CPBM);
 
 	__test_mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 0);
 	KUNIT_EXPECT_EQ(test, test_result[0], 0);