mhi: core: Remove incorrect macro for tre sizes

Remove unused macros for TRE sizes. This information is
now present in device tree.

Change-Id: Id3ca59c62d66ce8913e83fcba60e1a912cf146ea
Signed-off-by: Andrei Danaila <adanaila@codeaurora.org>
Signed-off-by: Tony Truong <truong@codeaurora.org>