MIPS: Revert "add support for buggy MT7621S core detection"

This reverts commit 6decd1aa. CPULAUNCH
register is not set properly by some bootloaders, causing a regression
until a bootloader change is made, which is hard if not impossible on
some embedded devices. Revert the change until a more robust core
detection mechanism that works on MT7621S routers such as Netgear R6220
as well as platforms like Digi EX15 can be made.

Link: https://lore.kernel.org/lkml/4d9e3b39-7caa-d372-5d7b-42dcec36fec7@kernel.org


Fixes: 6decd1aa ("MIPS: add support for buggy MT7621S core detection")
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Acked-by: Greg Ungerer <gerg@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>