cmake: arm: linker: remove usage of ld-specific ADDR() function

Remove usage of ld-specific ADDR function within the cmake linker
generator scripting. Since the linker generator scripting doesn't
support MPUs, we can simply set the __ramfunc_region_start symbol to be
equal to __ramfunc_start

Fixes #87200

Signed-off-by: Daniel DeGrasse <ddegrasse@tenstorrent.com>
(cherry picked from commit b84076a1)