helper/jim-nvp: avoid camelcase error by deprecated API

Commit b8e18d292e ("helper/jim-nvp: comply with coding style
[1/2]") tags as deprecated the old CamelCase API of jim-nvp, so
that old patches already in gerrit or in user's local git can
still build while dumping a deprecated message.

So far, we have not found any such case, so the deprecated API can
be safely dropped in preparation of v0.12.0-rc1.

Drop the compile flag "-Wno-error=deprecated-declarations" and the
deprecated API.

Change-Id: I52ce47eda69a51c2dd29aac15f16e285492d89b4
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7052
Tested-by: jenkins

configure.ac

@@ -806,7 +806,6 @@ AS_IF([test "x${gcc_wextra}" = "xyes"], [
   GCC_WARNINGS="${GCC_WARNINGS} -Wredundant-decls"
   GCC_WARNINGS="${GCC_WARNINGS} -Wpointer-arith"
   GCC_WARNINGS="${GCC_WARNINGS} -Wundef"
-  GCC_WARNINGS="${GCC_WARNINGS} -Wno-error=deprecated-declarations"
 ])
 AS_IF([test "x${gcc_werror}" = "xyes"], [
   GCC_WARNINGS="${GCC_WARNINGS} -Werror"