bpf, doc: Update KP's email in MAINTAINERS

Helps me use a single account to sign off and send patches use
appropriate email redirection without needing to update MAINTAINERS.
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201208214900.80684-1-kpsingh@kernel.org

MAINTAINERS

@@ -3237,7 +3237,7 @@ R:	Martin KaFai Lau <kafai@fb.com>
 R:	Song Liu <songliubraving@fb.com>
 R:	Yonghong Song <yhs@fb.com>
 R:	John Fastabend <john.fastabend@gmail.com>
-R:	KP Singh <kpsingh@chromium.org>
+R:	KP Singh <kpsingh@kernel.org>
 L:	netdev@vger.kernel.org
 L:	bpf@vger.kernel.org
 S:	Supported
@@ -3356,7 +3356,7 @@ F:	arch/x86/net/
 X:	arch/x86/net/bpf_jit_comp32.c
 
 BPF LSM (Security Audit and Enforcement using BPF)
-M:	KP Singh <kpsingh@chromium.org>
+M:	KP Singh <kpsingh@kernel.org>
 R:	Florent Revest <revest@chromium.org>
 R:	Brendan Jackman <jackmanb@chromium.org>
 L:	bpf@vger.kernel.org