target/nios2: fix page-fit instruction count

target/nios2: fix page-fit instruction count

This patch fixes calculation of number of the instructions
that fit the current page. It prevents creation of the translation
blocks that cross the page boundaries. It is required for deterministic
exception generation in icount mode.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <162072241046.823357.10485774346114851009.stgit@pasha-ThinkPad-X280>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>