xtensa: Avoid calling get_page_addr_code() from helper function

xtensa: Avoid calling get_page_addr_code() from helper function

The xtensa frontend calls get_page_addr_code() from its
itlb_hit_test helper function. This function is really part
of the TCG core's internals, and calling it from a target
helper makes it awkward to make changes to that core code.
It also means that we don't pass the correct retaddr to
tlb_fill(), so we won't correctly handle the case where
an exception is generated.

The helper is used for the instructions IHI, IHU and IPFL.

Change it to call cpu_ldb_code_ra() instead.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>