This reverts commit 947d1c7ecf.
lnx_platform.c doesn't exist in this branch since commit 54681238
renamed it to shared/drm_platform.c and added it to the BSD build.
Fixes build failures in CI of:
../hw/xfree86/os-support/meson.build:163:18: ERROR: File linux/lnx_platform.c does not exist.
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>