Cleanup the kernel SIMD code by removing kernel dependencies.
- Replace XSTATE_XSAVE with our own XSAVE implementation for all
kernels not exporting kernel_fpu{begin,end}(), see #13059
- Replace union fpregs_state by a uint8_t * buffer and get the size
of the buffer from the hardware via the CPUID instruction
- Replace kernels xgetbv() by our own implementation which was
already there for userspace.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes#13102
ce7a5dbf4b