speakup: Allow lower values for the flush parameter

Users needing it with the dectlk synth report that a 100ms flush delay
is still noticeable and prefer to set it to e.g. 10ms. This leaves the
default to 4000ms (since hitting it is a sign that the cable is faulty
and should be replaced), but allows to set it as short as 10ms.

Signed-off-by: Samuel Thibault <[e-mail]>
Link: https://lore.kernel.org/r/20220205232957.bc6o6yyt5hitg754@begin
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/accessibility/speakup/synth.c

···
 	{ TRIGGER, .u.n = {NULL, 20, 10, 2000, 0, 0, NULL } },
 	{ JIFFY, .u.n = {NULL, 50, 20, 200, 0, 0, NULL } },
 	{ FULL, .u.n = {NULL, 400, 200, 60000, 0, 0, NULL } },
-	{ FLUSH, .u.n = {NULL, 4000, 100, 4000, 0, 0, NULL } },
+	{ FLUSH, .u.n = {NULL, 4000, 10, 4000, 0, 0, NULL } },
 	V_LAST_VAR
 };