acpi/hmat: fix an uninitialized memory_target

The commit 665ac7e9 ("acpi/hmat: Register processor domain to its
memory") introduced an uninitialized "struct memory_target" that could
cause an incorrect branching.

drivers/acpi/hmat/hmat.c:385:6: warning: variable 'target' is used
uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]
        if (p->flags & ACPI_HMAT_MEMORY_PD_VALID) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/acpi/hmat/hmat.c:392:6: note: uninitialized use occurs here
        if (target && p->flags & ACPI_HMAT_PROCESSOR_PD_VALID) {
            ^~~~~~
drivers/acpi/hmat/hmat.c:385:2: note: remove the 'if' if its condition
is always true
        if (p->flags & ACPI_HMAT_MEMORY_PD_VALID) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/acpi/hmat/hmat.c:369:30: note: initialize the variable 'target'
to silence this warning
        struct memory_target *target;
                                    ^
                                     = NULL

Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Fixes: 665ac7e9 ("acpi/hmat: Register processor domain to its memory")
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>