ACPICA: Tables: Do not validate signature for dynamic table load

ACPICA commit d3c944f2cdc8c7e847b7942b1864f285189f7bce

Windows seems to allow arbitrary table signatures for Load/load_table
opcodes:
  ACPI BIOS Error (bug): Table has invalid signature [PRAD] (0x44415250)
So this patch removes dynamic load signature checks. However we need to
find a way to avoid table loading against tables like MADT. This is not
covered by this commit.

This Windows behavior has been validated on link #1. An end user bug
report can also be found on link #2.

This patch also includes simple cleanup for static load signature check
code. Reported by Ye Xiaolong, Fixed by Lv Zheng.

Link: https://github.com/acpica/acpica/commit/d3c944f2
Link: https://github.com/acpica/acpica/pull/121 [#1]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=118601

 [#2]
Reported-by: Ye Xiaolong <xiaolong.ye@intel.com>
Reported-by: Olga Uhina <olga.uhina@gmail.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>