parisc: Remove flush_user_dcache_range and flush_user_icache_range

The functions flush_user_dcache_range() and flush_user_icache_range()
are only used by the parisc signal handling code.  This code only needs
to flush a couple of lines, so the threshold check is unnecessary
overhead.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>