Option CONFIG_SENSORS_QENCODER might be configured even if SAMv7 qencoder
over timer counter is not used (for example encoder over GPIO is selected
with CONFIG_SAMV7_GPIO_ENC). This can cause compile warnings, also build
of sam_qencoder.c file is unnecessary in that case.
New hidden option CONFIG_SAMV7_QENCODER is added and automatically
selected if at least one timer counter is enabled for qencoder. Build
is triggered on this option.
Signed-off-by: Michal Lenc <michallenc@seznam.cz>