modules: fix some riscv module logic

The change which enabled the sdhci_fdt module build on riscv
inadvertently enabled the neta module as well. This driver is not needed
on this platform.

Move each entry to a respective identical conditional blocks.

MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Fixes:	e9dd9f95f8 ("riscv: Add the sdhci_fdt driver to the build")

sys/modules/Makefile

@@ -683,6 +683,7 @@ _irdma=		irdma
 .if !empty(OPT_FDT)
 _allwinner=	allwinner
 _if_cgem=	if_cgem
+_sdhci_fdt=	sdhci_fdt
 .endif
 .endif
 
@@ -726,14 +727,6 @@ _rockchip=	rockchip
 _imx=		imx
 .endif
 
-.if ${MACHINE_CPUARCH} == "aarch64" || ${MACHINE_CPUARCH} == "arm" || \
-    ${MACHINE_CPUARCH} == "riscv"
-.if !empty(OPT_FDT)
-_sdhci_fdt=	sdhci_fdt
-.endif
-_neta=		neta
-.endif
-
 .if ${MACHINE_CPUARCH} == "i386" || ${MACHINE_CPUARCH} == "amd64"
 _agp=		agp
 .if ${MACHINE_CPUARCH} == "i386" || !empty(COMPAT_FREEBSD32_ENABLED)
@@ -928,7 +921,8 @@ _nvram+=	powermac_nvram
 
 .if ${MACHINE_CPUARCH} == "arm" || ${MACHINE_CPUARCH} == "aarch64"
 _bcm283x_clkman=  bcm283x_clkman
-_bcm283x_pwm=  bcm283x_pwm
+_bcm283x_pwm=	bcm283x_pwm
+_neta=		neta
 .endif
 
 .if ${MACHINE_CPUARCH} == "amd64"