nvmem: core: Grammar fixes for help text

It's "an unsigned" but "a U".
Similarly, "an entry" but "a binary entry".

While at it, also drop superfluous articles for negative and zero.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200722100705.7772-6-srinivas.kandagatla@linaro.org


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