spi/pl022: Fix range checking for bits per word

pl022 ssp controller supports word lengths from 4 to 16 (or 32) bits.
Currently implemented checks were incorrect. It has following check

if (pl022->vendor->max_bpw >= 32)

which must be checking for <=.

Also error print message is incorrect, that prints "range is from 1 to
16".

Fix both these issues.

Signed-off-by: Vinit Shenoy <vinit.shenoy@st.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>