mpam: Fix uninitialized value

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7ZRRD



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Fix the following smatch warning:

drivers/acpi/arm64/mpam.c:219 acpi_mpam_parse_version() error: uninitialized
symbol 'ret'.

Fixes: b1e2f3d84839 ("[Backport] ACPI/MPAM: Adapt to Arm's MPAM ACPI table version 2")
Signed-off-by: Yu Liao <liaoyu15@huawei.com>