arm: stm32mp: bsec: remove unneeded test

Remove the test offs < 0 , as offs is unsigned.

This patch solves the warnings when compiling with W=1
on stm32mp1 board:

In function ‘stm32mp_bsec_read’:
arch/arm/mach-stm32mp/bsec.c:368:11: warning:
comparison of unsigned expression < 0 is always false [-Wtype-limits]
  368 |  if (offs < 0 || (offs % 4) || (size % 4))
      |           ^
In function ‘stm32mp_bsec_write’:
arch/arm/mach-stm32mp/bsec.c:405:11: warning:
comparison of unsigned expression < 0 is always false [-Wtype-limits]
  405 |  if (offs < 0 || (offs % 4) || (size % 4))
      |           ^

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Acked-by: Patrice Chotard <patrice.chotard@st.com>