accel/ivpu: Refactor BO creation functions

Rename BO allocate/create functions, so the code is more consistent.
There are now two matching buffer creation functions:
  - ivpu_bo_create_ioctl() - create a BO from user space
  - ivpu_bo_create() - create a BO from kernel space

ivpu_bo_alloc() is now only used to allocate struct ivpu_bo which better
matches its name.

Signed-off-by: Wachowski, Karol <karol.wachowski@intel.com>
Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240214081305.290108-8-jacek.lawrynowicz@linux.intel.com