ARM: mx51_defconfig: add new boards MACH_MX51_3DS and MACH_EUKREA_CPUIMX51

Further remove FIXED_PHY as it breaks the ethernet.
VGA_CONSOLE isn't selectable anymore since fb78b51c.
EXT3_DEFAULTS_TO_ORDERED defaults to y since aa32a796.
INOTIFY is gone since 2dfc1cae.
CONFIG_DETECT_SOFTLOCKUP is gone since e16bb1d7.
Enable TMPFS for udev.
KEYS is selected by NFS_USE_KERNEL_DNS

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>