Delay the attachment of children, when requested, until after interrutps are
running. This is often needed to allow children to run transactions on i2c or
spi busses. It's a common enough idiom that it will be useful to have its own
wrapper.
Reviewed by: ian
Differential Revision: https://reviews.freebsd.org/D21465
While here, call device_delete_children() to detach and dealloc all the
existent children and handle the child's detach errors properly.
Reported by: jenkins, hselasky, ian
Sponsored by: Rubicon Communications, LLC (Netgate)
Interrupt based driver, implements SPI mode and clock configuration.
Tested on espressobin and SG-3200.
Sponsored by: Rubicon Communications, LLC (Netgate)
