target/hppa: sar register allows only 5 bits on 32-bit CPU

target/hppa: sar register allows only 5 bits on 32-bit CPU

The sar shift amount register is limited to 5 bits when running
a 32-bit CPU. Strip off the remaining bits.

The interesting part is, that this register allows to detect at runtime
if a physical CPU is capable to execute PA2.0 (64-bit) instructions.

Signed-off-by: Helge Deller <deller@gmx.de>