target-xtensa: tests: pre-process tests linker script

target-xtensa: tests: pre-process tests linker script

Xtensa cores have configurable interrupt vectors and endiannes. This
information is needed to link executable images correctly for a specific
core configuration. Instead of hard-coding dc232 defaults pull endianness,
number of high-priority interrupts and location of vectors from the core
configuration and pass it through the C preprocessor.

While at it clean up tabs and align the initial stack on 16 bytes.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>