fix(drivers/mtd): fix MISRA issues and logic improvement
fix(drivers/mtd): fix MISRA issues and logic improvement

Fix MISRA issues and invert the spi_nor_ready status
to improve readability.
Remove an unneeded variable initialization.

Change-Id: I25a97fbd6c4389156b4f077b986019fa7c30a457
Signed-off-by: Lionel Debieve <432d923c5c9ef0a4663385d08cf92d35d2459feb@st.com>
Signed-off-by: Yann Gautier <e753f6969c288905606e3c07464886d4f1fc1be0@st.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware