mfd: si476x-cmd: Fix a bunch of incorrectly documented function names

Fixes the following W=1 kernel build warning(s):

 drivers/mfd/si476x-cmd.c:406: warning: expecting prototype for si476x_cmd_func_info(). Prototype was for si476x_core_cmd_func_info() instead
 drivers/mfd/si476x-cmd.c:437: warning: expecting prototype for si476x_cmd_set_property(). Prototype was for si476x_core_cmd_set_property() instead
 drivers/mfd/si476x-cmd.c:463: warning: expecting prototype for si476x_cmd_get_property(). Prototype was for si476x_core_cmd_get_property() instead
 drivers/mfd/si476x-cmd.c:525: warning: expecting prototype for si476x_cmd_dig_audio_pin_cfg(). Prototype was for si476x_core_cmd_dig_audio_pin_cfg() instead
 drivers/mfd/si476x-cmd.c:574: warning: expecting prototype for si476x_cmd_zif_pin_cfg(). Prototype was for si476x_core_cmd_zif_pin_cfg() instead
 drivers/mfd/si476x-cmd.c:631: warning: expecting prototype for si476x_cmd_ic_link_gpo_ctl_pin_cfg(). Prototype was for si476x_core_cmd_ic_link_gpo_ctl_pin_cfg() instead
 drivers/mfd/si476x-cmd.c:662: warning: expecting prototype for si476x_cmd_ana_audio_pin_cfg(). Prototype was for si476x_core_cmd_ana_audio_pin_cfg() instead
 drivers/mfd/si476x-cmd.c:697: warning: expecting prototype for si476x_cmd_intb_pin_cfg(). Prototype was for si476x_core_cmd_intb_pin_cfg_a10() instead
 drivers/mfd/si476x-cmd.c:742: warning: expecting prototype for si476x_cmd_am_rsq_status(). Prototype was for si476x_core_cmd_am_rsq_status() instead
 drivers/mfd/si476x-cmd.c:874: warning: expecting prototype for si476x_cmd_fm_seek_start(). Prototype was for si476x_core_cmd_fm_seek_start() instead
 drivers/mfd/si476x-cmd.c:905: warning: expecting prototype for si476x_cmd_fm_rds_status(). Prototype was for si476x_core_cmd_fm_rds_status() instead
 drivers/mfd/si476x-cmd.c:1050: warning: expecting prototype for si476x_cmd_am_seek_start(). Prototype was for si476x_core_cmd_am_seek_start() instead

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>