Replace mips/sentry5 with mips/broadcom
The delta between SENTRY5 and BCM was already small due to BCM being
derived from SENTRY5; re-integrating the two avoids the maintenance
overhead of keeping them both in sync with bhnd(4) changes.
- Re-integrate minor SENTRY5 deltas in bcm_machdep.c
- Modify uart_cpu_chipc to allow specifying UART debug/console flags via kenv and device hints.
- Switch SENTRY5 to std.broadcom
- Enabled CFI flash support for SENTRY5
Reviewed by: Michael Zhilin <mizkha@gmail.com> (Broadcom MIPS support)
Approved by: re (gjb), adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6897