[Why] Drop dead code for Linux. [How] Remove all IS_FPGA_MAXIMUS_DC and IS_DIAG_DC Reviewed-by: Ariel Bernstein <eric.bernstein@amd.com> Acked-by: Tom Chung <chiahsuan.chung@amd.com> Signed-off-by: Qingqing Zhuo <qingqing.zhuo@amd.com> Tested-by: Daniel Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>