crypto: kconfig: Fix config text for dm-req-crypt module

Text for dm-req-crypt module in kernelconfig menu shows as
"Crypt target support" which is same as for dm-crypt module. Fixing
this to reflect correct text for dm-req-crypt module.

Change-Id: I8eaa3ef71267609448a5082feab1810b28ab02e7
Signed-off-by: Dinesh K Garg <dineshg@codeaurora.org>