xtensa: fix default kernel load address

Make default kernel load address 0xd0003000 for MMUv2 cores and
0x60003000 for noMMU cores. Don't initialize MMU inside vmlinux for
predefined MMUv2 cores (it's noop anyway).

This fixes the following defconfig build error:
  arch/xtensa/kernel/built-in.o: In function `fast_alloca':
  (.text+0x99a): dangerous relocation: j: cannot encode: _WindowUnderflow12
  arch/xtensa/kernel/built-in.o: In function `fast_alloca':
  (.text+0x99d): dangerous relocation: j: cannot encode: _WindowUnderflow8
  arch/xtensa/kernel/built-in.o: In function `fast_alloca':
  (.text+0x9a0): dangerous relocation: j: cannot encode: _WindowUnderflow4
  arch/xtensa/kernel/built-in.o: In function `window_overflow_restore_a0_fixup':
  (.text+0x23a3): dangerous relocation: j: cannot encode: (.DoubleExceptionVector.text+0x104)
  arch/xtensa/kernel/built-in.o: In function `window_overflow_restore_a0_fixup':
  (.text+0x23c1): dangerous relocation: j: cannot encode: (.DoubleExceptionVector.text+0x104)
  arch/xtensa/kernel/built-in.o: In function `window_overflow_restore_a0_fixup':
  (.text+0x23dd): dangerous relocation: j: cannot encode: (.DoubleExceptionVector.text+0x104)

With this change all xtensa defconfigs build correctly.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>