qemu: Update to 6.1.0

* 6.1.0 release has NetBSD NVMM support.
* Fix NetBSD NVMM compile errors.
* Remove integrated Alpha patches.

Changelog:
Highlights include:

  * block: support for changing block node options after creation via
    'blockdev-reopen' QMP command
  * Crypto: more performant backend recommendations and improved documentation
  * I2C: emulation support for I2C muxes (pca9546, pca9548) and PMBus
  * TCG Plugins: now enabled by default, with new execlog and cache modelling
    plugins.
  * ARM: new board support for Aspeed (rainier-bmc, quanta-q7l1), npcm7xx
    (quanta-gbs-bmc), and Cortex-M3 (stm32vldiscovery) based machines
  * ARM: Aspeed support of Hash and Crypto Engine
  * ARM: emulation support for SVE2 (including bfloat16), integer matrix
    multiply accumulate operations, TLB invalidate in Outer Shareable domain,
    TLB range invalidate, and more.
  * PowerPC: pseries: support for detecting hotplug failures in newer guests
  * PowerPC: pseries: increased maximum CPU count
  * PowerPC: pseries: emulation support for some POWER10 prefixed instructions
  * PowerPC: new board support for Genesi/bPlan Pegasos II (pegasos2)
  * RISC-V: updates to OpenTitan platform support, including OpenTitan timer
  * RISC-V: support for virtio-vga
  * RISC-V: documentation improvements and general code cleanups/fixes
  * s390: emulation support for the vector-enhancements facility
  * s390: support for gen16 CPU models
  * x86: new Intel CPU model versions with support for XSAVES instruction
  * x86: added ACPI based PCI hotplug support for Q35 machine (now the default)
  * x86: improvements to emulation of AMD virtualization extensions
  * and lots more...

(ryoon)