sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

goldfish_rtc: Fix handling a local time RTC

The default QEMU config is to have the RTC in UTC. However, if run with
-rtc base=localtime (and wall_cmos_clock is set to match), the driver
fails to account for adjkerntz due to the use of CLOCKF_SETTIME_NO_ADJ.
Copy the same code used by other CLOCKF_SETTIME_NO_ADJ-using drivers
to fix this, namely manually subtracting utc_offset().

Fixes: d63a631e7244 ("Add Goldfish RTC device driver for RISC-V")
MFC after: 1 week

goldfish_rtc: Remove unused devclass argument to DRIVER_MODULE.

Add Goldfish RTC device driver for RISC-V

This device was originally used as part of the goldfish virtual hardware
platform used for emulating Android on QEMU, but is now also used as the
RTC for the RISC-V virt machine in QEMU. It provides a simple 64-bit
nanosecond timer exposed via a pair of memory-mapped 32-bit registers,
although only with 1s granularity.

Reviewed by: brooks (mentor), jhb (mentor), kp
Approved by: brooks (mentor), jhb (mentor), kp
Obtained from: CheriBSD
Differential Revision: https://reviews.freebsd.org/D25717