mISDN: remove unused struct 'bf_ctx'

'bf_ctx' appears unused since the original
commit 960366cf8dbb ("Add mISDN DSP").

Remove it.

Signed-off-by: Dr. David Alan Gilbert <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/isdn/mISDN/dsp_blowfish.c

···
  * crypto-api for faster implementation
  */
 
-struct bf_ctx {
-	u32 p[18];
-	u32 s[1024];
-};
-
 static const u32 bf_pbox[16 + 2] = {
 	0x243f6a88, 0x85a308d3, 0x13198a2e, 0x03707344,
 	0xa4093822, 0x299f31d0, 0x082efa98, 0xec4e6c89,