net: tftp: Add help for CONFIG_TFTP_BLOCKSIZE

Add help message for the CONFIG_TFTP_BLOCKSIZE default value,
as explain in tftp.c before migration in commit b618b3707633
("net: Convert CONFIG_TFTP_BLOCKSIZE to Kconfig")

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
1 file changed