module: Rework module_addr_{min,max}

__module_address() does an initial bound check before doing the
{list/tree} iteration to find the actual module. The bound variables
are nowhere near the mod_tree cacheline, in fact they're nowhere near
one another.

module_addr_min lives in .data while module_addr_max lives in .bss
(smarty pants GCC thinks the explicit 0 assignment is a mistake).

Rectify this by moving the two variables into a structure together
with the latch_tree_root to guarantee they all share the same
cacheline and avoid hitting two extra cachelines for the lookup.

While reworking the bounds code, move the bound update from allocation
to insertion time, this avoids updating the bounds for a few error
paths.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>