In previous code, the rsdp initialization is done in get_rsdp() api implicitly.
The function is called multiple times in following acpi table parsing functions
and the condition (rsdp == NULL) need to be added in each parsing function.
This is not needed since the panic would occur if rsdp is NULL when do acpi
initialization.
Tracked-On: #5626
Signed-off-by: Victor Sun <victor.sun@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>