manpage: Fix markup and parameter description for dirtyjtag_spi

The heading for the subsequent entry should start with `.SS`, the
`.BR` was probably spurious (led to missing whitespace) and the
parameter name is `spispeed`, the argument placeholder `frequency`.

Change-Id: Ie0ce51d5fcd1a45cd0362ed08d8992169184ab3d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73256
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jean THOMAS <virgule@jeanthomas.me>
1 file changed