Fix several MIPS/BCM-blocking bugs in bhnd(4) chipc

• Correct IRQ lines for UART (to fix IRQ lookup in future)
• Check device unit in resource assignment during chipc_add_child
• If chipc hint->size is RM_MAX_END, resource end should be same as window end
• Clear reference from resource list entry to resource in case of resource release
• Add CHIPC_GET_CAPS implementation
• Correct chipc flash constants (to be unshifted)
• Default implementation of get_attach_type should iterate over device tree
• Add default implementation for BHND_CHIPC_GET_CAPS usable by chipc grandchildren

Submitted by: Michael Zhilin <mizhka@gmail.com>
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6584