misc: pch_phub: Provide descriptions for 'chip' argument

misc: pch_phub: Provide descriptions for 'chip' argument

For some reason (probably copy 'n' paste) kerneldoc descriptions
were missing for all instances of 'chip'.  Providing them squashes
the following W=1 kernel build warnings:

 drivers/misc/pch_phub.c:145: warning: Function parameter or member 'chip' not described in 'pch_phub_read_modify_write_reg'
 drivers/misc/pch_phub.c:282: warning: Function parameter or member 'chip' not described in 'pch_phub_read_serial_rom'
 drivers/misc/pch_phub.c:296: warning: Function parameter or member 'chip' not described in 'pch_phub_write_serial_rom'
 drivers/misc/pch_phub.c:334: warning: Function parameter or member 'chip' not described in 'pch_phub_read_serial_rom_val'
 drivers/misc/pch_phub.c:350: warning: Function parameter or member 'chip' not described in 'pch_phub_write_serial_rom_val'
 drivers/misc/pch_phub.c:450: warning: Function parameter or member 'chip' not described in 'pch_phub_read_gbe_mac_addr'
 drivers/misc/pch_phub.c:462: warning: Function parameter or member 'chip' not described in 'pch_phub_write_gbe_mac_addr'

Cc: Masayuki Ohtak <masa-korg@dsn.okisemi.com>
Cc: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200701085853.164358-14-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>