ACPICA: iasl/Disassembler: Support ASL ElseIf operator

ACPICA commit 918a840d27d620942e0ecb69de320bb71ea86c5a

ElseIf is a macro that resolves to an Else..If in the AML byte code.
This support merges an Else followed immediately by an If to an
ASL ElseIf operator. Simplifies decoded ASL, especially for large
Switch statements.

This patch only applies to iasl, and is no-op for Linux kernel.

Link: https://github.com/acpica/acpica/commit/918a840d


Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>