soc/intel_adsp: Correct linker syntax for ancient binutils

Older binutils, like the (nine-year-old!) 2.23 version that powers
many Cadence XCC toolchains, happen not to support the "~" operator to
perform bitwise negation.  And they generate an absolutely hilarious
series of inscrutable error messages when they try to tell you this
fairly simple fact.

Just fold it into the constant.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>