drivers/sfi: sfi_acpi.c needs sysfs.h

drivers/sfi: sfi_acpi.c needs sysfs.h

sfi_acpi.c needs to include linux/sysfs.h for data types.

drivers/sfi/sfi_core.h:66: error: field 'attr' has incomplete type
drivers/sfi/sfi_acpi.c:179: warning: 'struct kobject' declared inside parameter list
drivers/sfi/sfi_acpi.c:179: warning: its scope is only this definition or declaration, which is probably not what you want
drivers/sfi/sfi_acpi.c:182: warning: type defaults to 'int' in declaration of '__mptr'
drivers/sfi/sfi_acpi.c:182: warning: initialization from incompatible pointer type

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>