LynxOS is no longer supported

LynxOS needed the do_bootm_lynxkdi() function that got removed in
7e713067ee ("Remove LYNX KDI remainders") - and that function needed
a lynxkdi_boot() function, where the last implementation had been
removed in 98f705c9ce ("powerpc: remove 4xx support") already. Looks
like this OS is definitely not supported anymore, so remove it from
the corresponding lists.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/README b/README
index 77782d0..5549849 100644
--- a/README
+++ b/README
@@ -2912,8 +2912,7 @@
 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
   4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
   LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
-  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
-  INTEGRITY).
+  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
   IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
   Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).