libplatsupport: Moved BIOS RSDP Parsing

Moved the parsing of the RSDP from BIOS to be handled at an
earlier step in the acpi initialisation procedure. Exported
the acpi_parse_table function from the walker code to parse
the rsdp table when initialising the acpi_t object.

libplatsupport: Modifications to RSDP parsing

Moved the parsing of the RSDP out of the table parsing procedure,
(_acpi_parse_tables). If the RSDP is not provided for ACPI
initialization, it will be searched for in the BIOS segment.
Modified the acpi_t struct to store the whole
RSDP object rather than the physical address of the object.

libplatsupport: Initialize ACPI with given RSDP

Enable ACPI initialization by passing an RSDP object rather
than searching for it within the BIOS section. Updated default
logical timer initialization to initialize the ACPI with a given
RSDP object.

fix licenses