[PARISC] Fix copy_user_page_asm to NOT access past end of page

2.6.12-rc2-pa3 fix copy_user_page_asm to NOT access past end of page.

My bad. /o\
Lamont confirmed that instructions following a conditional
branch are *alway* executed regardless if the branch is taken or not.
Unless they are nullified (which was missing in this case).

He also noted:
Conditional branches nullify on forward taken branch, and on
non-taken backward branch. Note that .+4 is a backwards branch.

This makes alot more sense than the giberish in the PA20 arch book.

Compiles and boots on both 64-bit (a500) and 32-bit (j6k).

Signed-off-by: Grant Grundler <grundler@parisc-linux.org>

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>