fsl-ifc: add missing include on ARM64

Need to include sched.h to fix the following compilation error
if FSL_IFC is enabled on ARM64 machine.

In file included from include/linux/mmzone.h:9:0,
                 from include/linux/gfp.h:5,
                 from include/linux/kmod.h:22,
                 from include/linux/module.h:13,
                 from drivers/memory/fsl_ifc.c:22:
drivers/memory/fsl_ifc.c: In function ‘check_nand_stat’:
include/linux/wait.h:165:35: error: ‘TASK_NORMAL’ undeclared (first use in this function)
 #define wake_up(x)   __wake_up(x, TASK_NORMAL, 1, NULL)
                                   ^
drivers/memory/fsl_ifc.c:136:3: note: in expansion of macro ‘wake_up’
   wake_up(&ctrl->nand_wait);
   ^
include/linux/wait.h:165:35: note: each undeclared identifier is reported only once for each function it appears in
 #define wake_up(x)   __wake_up(x, TASK_NORMAL, 1, NULL)
                                   ^
drivers/memory/fsl_ifc.c:136:3: note: in expansion of macro ‘wake_up’
   wake_up(&ctrl->nand_wait);
   ^

Analysis is as follows:
I put some instrumental code and get the
following .h files inclusion sequence:

In file included from ./arch/arm64/include/asm/compat.h:25:0,
                 from ./arch/arm64/include/asm/stat.h:23,
                 from include/linux/stat.h:5,
                 from include/linux/module.h:10,
                 from drivers/memory/fsl_ifc.c:23:
include/linux/sched.h:113:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘struct’
 struct sched_attr {
 ^

CONFIG_COMPAT=y is enabled while 39 and 48 bit VA is selected.
When 42 bit VA is selected, it does not enable CONFIG_COMPAT=y

In ./arch/arm64/include/asm/stat.h:23, it has
"#ifdef CONFIG_COMPAT"
"#include <asm/compat.h>"
"..."
"#endif"

Since ./arch/arm64/include/asm/stat.h does not
include ./arch/arm64/include/asm/compat.h,
then it will not include include/linux/sched.h
Hence we have to manually add "#include <linux/sched.h>"
in drivers/memory/fsl_ifc.c

Signed-off-by: Lijun Pan <Lijun.Pan@freescale.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>