soc: intel_adsp/cavs_v20: correct linker syntax for old binutils

Applying similar changes to cavs_v20 as in commit
8bc4539c:

  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: Daniel Leung <daniel.leung@intel.com>