realtek_mst_i2c_spi.c: Rename `PAGE_SIZE` macro

This fixes building with musl libc on alpine:amd64-v3.9.

Change-Id: I043e3d8c2d2498e94b5e7577a7378c8c3e0e6c81
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/53998
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
1 file changed