pmic: reword help text

Reword the help text for the pmic read and pmic write commands to better
match what's expected from the user.

Cc: Quentin Schulz <foss+uboot@0leil.net>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
diff --git a/cmd/pmic.c b/cmd/pmic.c
index 49a405f..c9e9730 100644
--- a/cmd/pmic.c
+++ b/cmd/pmic.c
@@ -225,6 +225,6 @@
 	"list          - list pmic devices\n"
 	"pmic dev [name]    - show or [set] operating PMIC device\n"
 	"pmic dump          - dump registers\n"
-	"pmic read address  - read byte of register at address\n"
-	"pmic write address - write byte to register at address\n"
+	"pmic read <reg>    - read byte of 'reg' register\n"
+	"pmic write <reg> <byte> - write 'byte' byte to 'reg' register\n"
 );