Documentation/Changes: Add bc in "Current Minimal Requirements" section

bc is mentioned lower in a dedicated section.
Yet it is useful to have all dependencies listed in
"Current Minimal Requirements" section.
Signed-off-by: NBenoit Lemarchand <benoit.lemarchand@gmail.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/Changes

@@ -44,6 +44,7 @@ o  grub                   0.93                    # grub --version || grub-insta
 o  mcelog                 0.6                     # mcelog --version
 o  iptables               1.4.2                   # iptables -V
 o  openssl & libcrypto    1.0.1k                  # openssl version
+o  bc                     1.06.95                 # bc --version
 
 
 Kernel compilation