LoongArch: Fix section mismatch due to acpi_os_ioremap()

Now acpi_os_ioremap() is marked with __init because it calls memblock_
is_memory() which is also marked with __init in the !ARCH_KEEP_MEMBLOCK
case. However, acpi_os_ioremap() is called by ordinary functions such
as acpi_os_{read, write}_memory() and causes section mismatch warnings:

WARNING: modpost: vmlinux.o: section mismatch in reference: acpi_os_read_memory (section: .text) -> acpi_os_ioremap (section: .init.text)
WARNING: modpost: vmlinux.o: section mismatch in reference: acpi_os_write_memory (section: .text) -> acpi_os_ioremap (section: .init.text)

Fix these warnings by selecting ARCH_KEEP_MEMBLOCK unconditionally and
removing the __init modifier of acpi_os_ioremap(). This can also give a
chance to track "memory" and "reserved" memblocks after early boot.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/Kconfig

@@ -39,6 +39,7 @@ config LOONGARCH
 	select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPTION
 	select ARCH_INLINE_SPIN_UNLOCK_IRQ if !PREEMPTION
 	select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
+	select ARCH_KEEP_MEMBLOCK
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select ARCH_SPARSEMEM_ENABLE

arch/loongarch/include/asm/acpi.h

@@ -15,7 +15,7 @@ extern int acpi_pci_disabled;
 extern int acpi_noirq;
 
 #define acpi_os_ioremap acpi_os_ioremap
-void __init __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
+void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
 
 static inline void disable_acpi(void)
 {

arch/loongarch/kernel/acpi.c

@@ -48,7 +48,7 @@ void __init __acpi_unmap_table(void __iomem *map, unsigned long size)
 	early_memunmap(map, size);
 }
 
-void __init __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
+void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
 {
 	if (!memblock_is_memory(phys))
 		return ioremap(phys, size);