spi: omap2-mcspi: remove several redundant variables

Variable count, l, mcspi and spi_cntrl are being assigned but are
never used hence they are redundant and can be removed.

Cleans up clang warnings:
warning: variable 'count' set but not used [-Wunused-but-set-variable]
warning: variable 'l' set but not used [-Wunused-but-set-variable]
warning: variable 'mcspi' set but not used [-Wunused-but-set-variable]
warning: variable 'spi_cntrl' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>