exec: fix TB invalidation after breakpoint insertion/deletion

tb_invalidate_phys_addr has to be called with the exact physical address of
the breakpoint we add/remove, not just the page's base address.
Otherwise we easily fail to flush the right TB.

This breakage was introduced by the commit f3705d5329 "memory: make
phys_page_find() return an unadjusted".

This appeared to work for some guest architectures because their
cpu_get_phys_page_debug implementation returns full translated physical
address, not just the base of the TARGET_PAGE_SIZE-sized page.

Reported-by: TeLeMan <geleman@gmail.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
