doc: Fixed consistency of Mbed term

Fixed the consistency of the case used for the Mbed term.

Signed-off-by: Francesco Servidio <francesco.servidio@nordicsemi.no>
diff --git a/docs/ecdsa.md b/docs/ecdsa.md
index 18ba0cf..bb2e376 100644
--- a/docs/ecdsa.md
+++ b/docs/ecdsa.md
@@ -4,7 +4,7 @@
 shortcut was taken, and these signatures were padded to make them
 always a fixed length.  Unfortunately, this padding was done in a way
 that is not easily reversible.  Some crypto libraries are fairly
-strict about the formatting of the ECDSA signature (specifically, mbed
+strict about the formatting of the ECDSA signature (specifically, Mbed
 TLS).  This currently means that the ECDSA SECP224R1 (EC) signature
 checking code will fail to boot about 1 out of every 256 images,
 because the signature itself will end in a 0x00 byte, and the code
@@ -43,7 +43,7 @@
     without padding), and the existing EC implementation will begin
     accepting padded and unpadded signatures.
 
-  - An mbed TLS implementation of EC256 can be added, but will require
+  - An Mbed TLS implementation of EC256 can be added, but will require
     the `--no-pad-sig` signature to be able to boot all generated
     images (without the argument 3 of out 4 images generated will have
     padding, and be considered invalid).