DynamicTablesPkg: Fix entry point param definition

DynamicTablesPkg: Fix entry point param definition

VS2017 reports 'warning C4028: formal parameter 2 different
from declaration' for the library constructor and destructor
interfaces for the Generator modules. VS2017 compiler also
reports similar warnings for the DXE entry points.

Remove the CONST qualifier for the SystemTable pointer (the
second parameter to the constructor/destructor/DXE Entry
point) to make it compatible with the formal declaration.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>