x86/crypto: Designate maintainer for SHA-1/256/512

 multibuffer driver

Even though I created the original implementation of SHA1 multibuffer
driver, Megha extended it to SHA256 and SHA512 and she is now maintaining
the code for SHA1/SHA256/SHA512 multi-buffer driver.

Add the entry in the MAINTAINERS file so any update patch can find
its way properly to Megha.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>