Internal-fn: Add FLOATN support for l/ll round and rint [PR/112432]

Internal-fn: Add FLOATN support for l/ll round and rint [PR/112432]

The defined DEF_EXT_LIB_FLOATN_NX_BUILTINS functions should also
have DEF_INTERNAL_FLT_FLOATN_FN instead of DEF_INTERNAL_FLT_FN for
the FLOATN support. According to the glibc API and gcc builtin, we
have below table for the FLOATN is supported or not.

+---------+-------+-------------------------------------+
|         | glibc | gcc: DEF_EXT_LIB_FLOATN_NX_BUILTINS |
+---------+-------+-------------------------------------+
| iceil   | N     | N                                   |
| ifloor  | N     | N                                   |
| irint   | N     | N                                   |
| iround  | N     | N                                   |
| lceil   | N     | N                                   |
| lfloor  | N     | N                                   |
| lrint   | Y     | Y                                   |
| lround  | Y     | Y                                   |
| llceil  | N     | N                                   |
| llfllor | N     | N                                   |
| llrint  | Y     | Y                                   |
| llround | Y     | Y                                   |
+---------+-------+-------------------------------------+

This patch would like to support FLOATN for:
1. lrint
2. lround
3. llrint
4. llround

The below tests are passed within this patch:
1. x86 bootstrap and regression test.
2. aarch64 regression test.
3. riscv regression tests.

	PR target/112432

gcc/ChangeLog:

	* internal-fn.def (LRINT): Add FLOATN support.
	(LROUND): Ditto.
	(LLRINT): Ditto.
	(LLROUND): Ditto.

Signed-off-by: Pan Li <pan2.li@intel.com>