iscsi_ibft: make ISCSI_IBFT dependson ACPI instead of ISCSI_IBFT_FIND

iscsi_ibft can use ACPI to find the iBFT entry during bootup,
currently, ISCSI_IBFT depends on ISCSI_IBFT_FIND which is
a X86 legacy way to find the iBFT by searching through the
low memory. This patch changes the dependency so that other
arch like ARM64 can use ISCSI_IBFT as long as the arch supports
ACPI.

ibft_init() needs to use the global variable ibft_addr declared
in iscsi_ibft_find.c. A #ifndef CONFIG_ISCSI_IBFT_FIND is needed
to declare the variable if CONFIG_ISCSI_IBFT_FIND is not selected.
Moving ibft_addr into the iscsi_ibft.c does not work because if
ISCSI_IBFT is selected as a module, the arch/x86/kernel/setup.c won't
be able to find the variable at compile time.
Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/firmware/Kconfig

@@ -170,7 +170,7 @@ config DMI_SCAN_MACHINE_NON_EFI_FALLBACK
 
 config ISCSI_IBFT_FIND
 	bool "iSCSI Boot Firmware Table Attributes"
-	depends on X86 && ACPI
+	depends on X86 && ISCSI_IBFT
 	default n
 	help
 	  This option enables the kernel to find the region of memory
@@ -181,7 +181,8 @@ config ISCSI_IBFT_FIND
 config ISCSI_IBFT
 	tristate "iSCSI Boot Firmware Table Attributes module"
 	select ISCSI_BOOT_SYSFS
-	depends on ISCSI_IBFT_FIND && SCSI && SCSI_LOWLEVEL
+	select ISCSI_IBFT_FIND if X86
+	depends on ACPI && SCSI && SCSI_LOWLEVEL
 	default	n
 	help
 	  This option enables support for detection and exposing of iSCSI

drivers/firmware/iscsi_ibft.c

@@ -93,6 +93,10 @@ MODULE_DESCRIPTION("sysfs interface to BIOS iBFT information");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(IBFT_ISCSI_VERSION);
 
+#ifndef CONFIG_ISCSI_IBFT_FIND
+struct acpi_table_ibft *ibft_addr;
+#endif
+
 struct ibft_hdr {
 	u8 id;
 	u8 version;