Corruption of register %o5 in window underflow trap handler

[Sebastian Huber]

The window underflow trap handler uses %i5 which destroys %o5 of the calling context.

Bug introduced by [0d3b5d47429effb350448d9e9123a67db722109f/rtems].

[Daniel Hellstrom <daniel@…>]

In 6c4aaf4f3167a9ca2eb2b1ae9b87381a03cb8aa1/rtems:

sparc: Fix window underflow trap handler

The window underflow trap handler used %i5 which destroyed the %o5 of
the calling context. Bug introduced by
0d3b5d47429effb350448d9e9123a67db722109f.

Go back to the pre 0d3b5d47429effb350448d9e9123a67db722109f behaviour
and use the two unused instructions in the trap vector to optimize a
bit.

Update #2651.

[Daniel Hellstrom <daniel@…>]

In 33de2037f6007f6adf90514dbc98158a473476fc/rtems:

sparc: Fix window underflow trap handler

The window underflow trap handler used %i5 which destroyed the %o5 of
the calling context. Bug introduced by
0d3b5d47429effb350448d9e9123a67db722109f.

Go back to the pre 0d3b5d47429effb350448d9e9123a67db722109f behaviour
and use the two unused instructions in the trap vector to optimize a
bit.

Close #2651.