mvpp2: suppress warning

Remove some unreachable code, so to suppress this warning:

drivers/net/ethernet/marvell/mvpp2/mvpp2_prs.c: In function ‘mvpp2_prs_tcam_first_free’:
drivers/net/ethernet/marvell/mvpp2/mvpp2_prs.c:397:10: warning: comparison is always false due to limited range of data type [-Wtype-limits]
  397 |  if (end >= MVPP2_PRS_TCAM_SRAM_SIZE)
      |          ^~

Fixes: 3f518509 ("ethernet: Add new driver for Marvell Armada 375 network unit")
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>