mmc-utils: properly set sparse option

mmc-utils: properly set sparse option

Commit [1] fixes the conditional invocation of sparse properly handling
the corresponding 'C' option. Hence, the related change in the
EXTRA_OEMAKE (i.e. C=0).

[1] https://web.git.kernel.org/pub/scm/utils/mmc/mmc-utils.git/commit/?id=a89cba2a0f8c6a19aa6b804877241170f5b6bdd2

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>