RISC-V: ACPI: Fix acpi_os_ioremap to return iomem address

acpi_os_ioremap() currently is a wrapper to memremap() on
RISC-V. But the callers of acpi_os_ioremap() expect it to
return __iomem address and hence sparse tool reports a new
warning. Fix this issue by type casting to  __iomem type.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307230357.egcTAefj-lkp@intel.com/
Fixes: a91a9ff ("RISC-V: Add support to build the ACPI core")
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230724100346.1302937-1-sunilvl@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: vlsunil

arch/riscv/include/asm/acpi.h

@@ -19,7 +19,7 @@ typedef u64 phys_cpuid_t;
 #define PHYS_CPUID_INVALID INVALID_HARTID
 
 /* ACPI table mapping after acpi_permanent_mmap is set */
-void *acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
+void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
 #define acpi_os_ioremap acpi_os_ioremap
 
 #define acpi_strict 1	/* No out-of-spec workarounds on RISC-V */

arch/riscv/kernel/acpi.c

@@ -215,9 +215,9 @@ void __init __acpi_unmap_table(void __iomem *map, unsigned long size)
 	early_iounmap(map, size);
 }
 
-void *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
+void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
 {
-	return memremap(phys, size, MEMREMAP_WB);
+	return (void __iomem *)memremap(phys, size, MEMREMAP_WB);
 }
 
 #ifdef CONFIG_PCI