misc: Fix build error about missing PAGE_SIZE

misc: Fix build error about missing PAGE_SIZE

This patch fixes the following build error:

  CC libc/misc/internals/__h_errno_location.os
  CC libc/misc/internals/parse_config.os
libc/misc/internals/parse_config.c: In function
'bb_get_chunk_with_continuation':
libc/misc/internals/parse_config.c:77: error: 'PAGE_SIZE' undeclared (first use in this function)
libc/misc/internals/parse_config.c:77: error: (Each undeclared identifier is reported only once
libc/misc/internals/parse_config.c:77: error: for each function it appears in.)
make[2]: *** [libc/misc/internals/parse_config.os] Error 1

Signed-off-by: Abdoulaye Walsimou Gaye <awg@embtoolkit.org>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>