intelspi: Add support for ddb/kdb -compatible polled mode

Required for Apple and Microsoft -compatible HID-over-SPI drivers.

Most logic was already implemented in commit 3c0867343819
"spibus: extend API: add cs_delay ivar, KEEP_CS and NO_SLEEP flags".
It dissallowed driver sleeps in the interrupt context. This commit
extends this feature to handle ddb/kdb context with following:

• Skip driver locking if SPI functions were called from kdb/ddb.
• Reinitialize controller if kdb/ddb initiated SPI transfer has interrupted another already running one. Does not work very reliable yet.

Reviewed by: manu
Differential Revision: https://reviews.freebsd.org/D41247