tests: Bluetooth: df: Fix wrong max antenna switch pattern len config

Due to change in Kconfig CONFIG_BT_CTLR_DF_MAX_ANT_SW_PATTERN_LEN
the Kconfigs in tests were wrong and tests were not building.
The commit sets the max antenna switch pattern length to actual
maximum value.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>