open_eth: fix number of RX and TX buffers

There's only 16K buffer memory, thus there may be at most 8 buffers
(4 TX + 4 RX) 1.5K each.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: fix UART base addr

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: reload register values after windowbase SR initialization

According to xtensa ISA windowbase reset value is undefined.
Re-initialize a0 and a3 after windowbase initialization.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: fix kernel entry code in the do_bootm_linux

Without this fix the following code is generated for the last asm block
of the do_bootm_linux function, which clobbers a3 just before it is
used:

d7f7265a:       022d            mov.n   a2, a2
d7f7265c:       023d            mov.n   a3, a2
d7f7265e:       0003a0          jx      a3

Fix it by declaring a2 and a3 registers as clobbered. Asm input
operands are guaranteed not to use any of the clobbered registers.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: add FDT support

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: add KC705 board

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
xtensa: update FSF config

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>