ALSA: qc_audio_offload: rename dma/iova/va/cpu/phys variables

ALSA: qc_audio_offload: rename dma/iova/va/cpu/phys variables

While trying to understand a bug in the audio offload code, I had
to spend extra time due to unfortunate nameing of local variables
and struct members.

Change these to more conventional names that reflect the actual
usage:

 - pointers to the CPU virtual addresses of a dma buffer get a
   _cpu suffix to disambiguate them for MMIO virtual addresses

 - MMIO virtual addresses that are mapped explicitly through
   the IOMMU get a _iova suffix consistently, rather than a
   mix of iova and va.

 - DMA addresses (dma_addr_t) that are in a device address
   space (linear or IOMMU) get a _dma suffix in place of the
   _pa suffix.

 - CPU physical (phys_addr_t) addresses get a _pa suffix.
   There is still a mixup with dma addresses here that I address
   in another patch.

No functional changes are intended here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250513123442.159936-2-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>