accel/ivpu: Fix wrong register read in LNL failure diagnostics

accel/ivpu: Fix wrong register read in LNL failure diagnostics

diagnose_failure_lnl() read VPU_HW_BTRS_MTL_INTERRUPT_STAT instead of
VPU_HW_BTRS_LNL_INTERRUPT_STAT, which on LNL and newer parts is a
different register with a different bit layout, so failure diagnostics
decoded the wrong register and reported a bogus error cause.
Read the LNL interrupt status register instead.

Fixes: 8a27ad81f7d3 ("accel/ivpu: Split IP and buttress code")
Reviewed-by: Andrzej Kacprowski <andrzej.kacprowski@linux.intel.com>
Signed-off-by: Karol Wachowski <karol.wachowski@linux.intel.com>
Link: https://patch.msgid.link/20260710101331.1899505-1-karol.wachowski@linux.intel.com