accel/ivpu: Rename VPU to NPU in message strings

VPU was renamed to NPU but due to large overhead of renaming
all the sources only user visible messages are being updated.

Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240214081305.290108-9-jacek.lawrynowicz@linux.intel.com