Compiler warning in trng_api.c with K64F

[JanneKiiskila]

Description

• Type: Bug
• Compiler warning - unused variable "ret"
• Priority: Minor

---

Bug

Target
K64F

Toolchain:
GCC_ARM

Toolchain version:
N/A

mbed-cli version:
0.9.10

meed-os sha:
7829b2f

official release 5.2.0, 5.2.1

DAPLink version:

Expected behavior

Actual behavior

Steps to reproduce

mbed compile -m K64F -t GCC_ARM -c

-- remove the unused variable ret, simple as that to fix.