Don't require a power up command in flash simulation model

We shouldn't need to send a power up command to the flash, and
Microwatt doesn't send one.

verilog/dv/caravel/spiflash.v

diff --git a/verilog/dv/caravel/spiflash.v b/verilog/dv/caravel/spiflash.v
index 1917933..29dde43 100644
--- a/verilog/dv/caravel/spiflash.v
+++ b/verilog/dv/caravel/spiflash.v
@@ -63,7 +63,7 @@
 	reg [7:0] spi_out;
 	reg spi_io_vld;
 
-	reg powered_up = 0;
+	reg powered_up = 1;
 
 	localparam [3:0] mode_spi         = 1;
 	localparam [3:0] mode_dspi_rd     = 2;