soc/intel_adsp: fix typo in L1EXP definition

The field offset is incorrect, L1EXP is at bit 24 and L1ETP at bit 25.

Fixes: cc6e9c09 ("soc/intel_adsp: Low level HDA driver and tests")
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>