nandwrite: fix build when long options are disabled

The Required_argument macro is only defined when long options are enabled.
Fixes the following build error:

miscutils/nandwrite.c: In function 'nandwrite_main':
miscutils/nandwrite.c:120:10: error: expected ',' or ';' before 'Required_argument'

Reported-by: Christian Kästner <kaestner at cs.cmu.edu>
Signed-off-by: Baruch Siach <baruch at tkos.co.il>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
nanddump: don't show --bb in usage when disabled

The --bb options now depends on LONG_OPTS. Omit mentions of --bb from usage
text when LONG_OPTS is disabled.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>