arm64: dts: imx93: update default value for snps,clk-csr

[ Upstream commit 109f256285dd6a5f8c3bd0d80d39b2ccd4fe314e ]

For the i.MX93 SoC, the default clock rate for the IP of STMMAC EQOS is
312.5 MHz. According to the following mapping table from the i.MX93
reference manual, this clock rate corresponds to a CSR value of 6.

 0000: CSR clock = 60-100 MHz; MDC clock = CSR clock/42
 0001: CSR clock = 100-150 MHz; MDC clock = CSR clock/62
 0010: CSR clock = 20-35 MHz; MDC clock = CSR clock/16
 0011: CSR clock = 35-60 MHz; MDC clock = CSR clock/26
 0100: CSR clock = 150-250 MHz; MDC clock = CSR clock/102
 0101: CSR clock = 250-300 MHz; MDC clock = CSR clock/124
 0110: CSR clock = 300-500 MHz; MDC clock = CSR clock/204
 0111: CSR clock = 500-800 MHz; MDC clock = CSR clock/324

Fixes: f2d03ba9

 ("arm64: dts: imx93: reorder device nodes")
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>