analyzer: fix -Wanalyzer-allocation-size false +ve on Linux kernel's round_up macro...

analyzer: fix -Wanalyzer-allocation-size false +ve on Linux kernel's round_up macro [PR113654]

gcc/analyzer/ChangeLog:
	PR analyzer/113654
	* region-model.cc (is_round_up): New.
	(is_multiple_p): New.
	(is_dubious_capacity): New.
	(region_model::check_region_size): Move usage of size_visitor into
	is_dubious_capacity.

gcc/testsuite/ChangeLog:
	PR analyzer/113654
	* c-c++-common/analyzer/allocation-size-pr113654-1.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>