libnvdimm/nfit_test: Fix acpi_handle redefinition

libnvdimm/nfit_test: Fix acpi_handle redefinition

After commit 62974fc389b3 ("libnvdimm: Enable unit test infrastructure
compile checks"), clang warns:

In file included from
../drivers/nvdimm/../../tools/testing/nvdimm/test/iomap.c:15:
../drivers/nvdimm/../../tools/testing/nvdimm/test/nfit_test.h:206:15:
warning: redefinition of typedef 'acpi_handle' is a C11 feature
[-Wtypedef-redefinition]
typedef void *acpi_handle;
              ^
../include/acpi/actypes.h:424:15: note: previous definition is here
typedef void *acpi_handle;      /* Actually a ptr to a NS Node */
              ^
1 warning generated.

The include chain:

iomap.c ->
    linux/acpi.h ->
        acpi/acpi.h ->
            acpi/actypes.h
    nfit_test.h

Avoid this by including linux/acpi.h in nfit_test.h, which allows us to
remove both the typedef and the forward declaration of acpi_object.

Link: https://github.com/ClangBuiltLinux/linux/issues/660
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20190918042148.77553-1-natechancellor@gmail.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>