regexdev: fix section attribute of symbols

regexdev: fix section attribute of symbols

The functions used by the drivers must be internal,
while the function and variables used in inline functions
must be experimental.

These are the changes done in the shared library:
- DF .text  Base          rte_regexdev_get_device_by_name
+ DF .text  INTERNAL      rte_regexdev_get_device_by_name
- DF .text  Base          rte_regexdev_register
+ DF .text  INTERNAL      rte_regexdev_register
- DF .text  Base          rte_regexdev_unregister
+ DF .text  INTERNAL      rte_regexdev_unregister
- DF .text  Base          rte_regexdev_is_valid_dev
+ DF .text  EXPERIMENTAL  rte_regexdev_is_valid_dev
- DO .bss   Base          rte_regex_devices
+ DO .bss   EXPERIMENTAL  rte_regex_devices
- DO .bss   Base          rte_regexdev_logtype
+ DO .bss   EXPERIMENTAL  rte_regexdev_logtype

Because these symbols were exported in the default section in DPDK 21.11,
any change in these functions would be seen as incompatible
by the ABI compatibility check.
An exception rule is added for this experimental library,
so the ABI check will skip it until the next ABI version.

Fixes: bab9497ef78b ("regexdev: introduce API")
Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Ori Kam <orika@nvidia.com>