greybus: fix typos in GREYBUS/GREYBUS_ES2 help text

Fix typos ("an" -> "a", "chose" -> "choose") in Kconfig

Signed-off-by: Zenyu Sy <zenyu@tuta.io>
Link: https://lore.kernel.org/r/20200426060048.14019-1-zenyu@tuta.io


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>